While Flacco's regression is certainly a massive factor in why the offense is a clusterfuck, that's not the best justification to let Marty off the hook. I'm a believer that he's getting blamed too much but there are some clear problems with this comparison.
I don't believe that bringing up Marty's past successes absolves him from any blame at all... Which, he deserves some. Todd Haley would not have this group, as untalented/depleted as it as, be playing like dogshit.
Here's why I think bringing up Marty's past is a significantly flawed reason to absolve him from any blame.
1. Our personel is nowhere near as good as several of the pieces on his Eagles and Niners teams. Maclin may be a commonality between us and the Eagles, but he was better during Marty's tenure than he is now, partially because injuries have taken a little bit of a toll on him(even though Maclin is still a pretty good WR). Throughout Marty's time there Marty has had the luxury of working with consistently good offensive lines(our oline may have it's bright moments, but it's very inconsistent) and (with the exception of when he started out in 2006, when it was still more of a running league) and a significantly better talent pool at skill positions thank frankly makes me jelous. But there were points Marty had an early in his career Maclin who was a #1 WR basically from the moment he took the field as a rookie(thank you for helping me win my fantasy league that year), Desean Jackson was the league's most explosive player early on in his career and arguably the best pure deep threat I've ever seen. Brent Celek was a really talented TE, and LJ Smith early on was underrated. Jason Avant was a damn good possesion WR, and Marty benefitted from having two pro bowl caliber running backs in Brian Westbrook and eventually Lesean McCoy. The talent really isn't comparable over those two teams. Eagles have us beat by a country mile even if they didn't get some of these guys until later on. Let's be real, while Flacco does our WRs no favors whatsoever, it's not like we have an enviable recieving corps. On paper it's talented, it's not getting open consistently or performing.
Oh.. And with the niners? Supporting cast was probably even better. Hall of Fame QB Steve Young was still an elite player in 1997 and 1998 until he was forced to retire in 1999. Jeff Garcia then proceeded to benefit greatly afterwards from what is arguably the greatest WR tandem in NFL history. Young was an elite player before then. And then you had Garrison Hearst who was a pro bowler(when the pro bowl still mattered and it was a rushing league still), young and budding stud and future hall of famer Terell Owens. When Hearst got hurt, Charlie Garner came in.. Was a also a pro bowler. Then there was also Jerry Rice, the greatest WR of all time, who was still a damn good player in 1998 and 1999(1997 I'm pretty sure he got hurt) and then 2000. Those niners squads had 3 pro bowl offensive linemen at different points as well. I'll take that over anything we have.. Hell I'll just take Jerry Rice or TO. No wonder they had a top ten offense there. Young, Rice, TO, with a good oline and a pro bowl running back in Hears and another to replace him in Garner? I'm very jealous.
Completely ignoring the context behind that is omitting important facts. Of course Marty's offenses were going to be more successful with those supporting casts. I could throw to a WR tandem of Terrell Owens and Jerry Rice and I have a shit noodle arm. As bad as Flacco has been struggling, we'd be at the very least a middle of the pack offense if we had some better talent across the board. Most offensive coordinators would suceed with some of the talent Marty has had access to throughout his career.
2. This claim omits an important fact when it comes to the Eagles. Marty had a guy named Andy Reid as his boss. An offensive genius by every sense of the word who is notorious for being a pretty QB friendly offensive mind as well. Sure, in 2006 Marty was "promoted" as the primary playcaller. But do you really think that Reid wouldn't intervene and/or play a significant role in the offense's production/scheme? It's important to make note of this fact, as even when Marty was calling the plays, Andy Reid's fingerprints were all over the offense(as it is to this day with the Cheifs). That's akin to giving Rick Dennison significant credit when Gary Kubiak was his boss and those Texan offenses had success, or whoever the current OC is for the Saints for what is clearly Sean Payton's well oiled machine, or conversely giving Matt Patricia(though he's a good defensive mind in his own right) credit for a Bill Bellicheck schemed defense. I mean does anybody even know who the current offensive coordinators of the Cheifs and the Saints are right now without looking them up? How about the current OC for the Rams and their newly rejuvenated offense(yes, they have one. McVay is not listed as their OC). I'm sure all of these coordinators do play a role in playcalling and gameplanning, but let's be clear: Andy Reid had a significant say and to think otherwise is honestly naive. Here, we are at a massive disadvantage of having a special teams guy as our head coach. And while Harbaugh is a good coach he doesn't have someone else to keep him in check(and I really don't think Roman does have that privevelge but agree to disagree). This was a fact that even I did not account for last year(frankly, I was just happy to be rid of Trestman.. And he's been better than Trestman fwiw so he was an upgrade). But solely giving Marty all the credit for those fantastic offenses of his is moot. He had elite talent at points with both the niners and eagles and one of the best offensive minds since the turn of the century in Andy Reid.
3. Saying that people can't blame Marty because he was a previously successful OC is akin to saying that Peyton Manning was still an elite QB in 2015-2016 because he had won a super bowl previously, and is one of the greatest quarterbacks ever. Or saying that the currently unemployed Norv Turner is still an elite offensive mind because he won two Super Bowls in the 1990s. Or saying that Rex Ryan would still be a great DC despite his defenses (which were talented btw) struggling this decade because his defense has adapted very poorly to the modern NFL. I don't necessarily think that Marty was ever in the camp of anybody above, but it's a weaker claim than most think. The game has passed Norv Turner and Rex Ryan by. They could not adapt(which is a shame I liked both o them). Marty isn't quite this extreme, though he is clearly part of the issue. Even going back to last season his situational football has been... mind boggling to say the least. At times he will call a very good play, but for every one of those, there's two or three more plays where you just bang your head against the wall.
4. I don't think Marty is incompetent. He's just not a good fit here. With Joe especially. Schematically I think we have significant issues.
@Truth and I were discussing the problems with the scheme as well several months for the Dennis Pitta injury. And yes, I do think Pitta's comments hold some weight. He was in the huddle as recently as a few months ago before he sadly reinjured his hip(and the rebuttal was total BS fwiw. We all know that Harbaugh is esentially a politician that's not actually in congress. He was going to say something to cover his ass after being exposed). I don't think the offense is specifically as basic as Pitta indicated, but you could tell that he was displeased. Which is saying something. Flacco constantly feeding him in 2016 made him a lot of money via incentives. Why be angry? There has to be some semblance of truth to what he said, and he's as reliable as source as it gets. He is also predictable.
@Jacquouille has pointed this out and frankly there are plays where even I could see the play coming from a mile away and I know NOTHING ABOUT ANYTHING. For these reasons, I do want him gone. He's not THE problem, but he's not making the situation better as a whole..
Marty is a part of the problem. Is he as significant as Flacco? Possibly. We won't know really until he was removed from the equation. I personally think the biggest issue of this offense is the shit/depleted personal. I've made that clear. But holding Marty accountable is not unfair. I think it's clear that he's part of the problem. Sad news is. He's not going anywhere until Harbaugh is gone.
Oh look.. Another Novel.
TLDR;
1. Marty's offenses with the Eagles and Niners had a good amount of talent. It wasn't flushed with elite talent, but they were a hell of a lot better than we were. Of course he'd had significant success.
2. Andy Reid clearly played a massive role in his successes with the Eagles. Marty probably deserves some credit, but Reid clearly has his finger prints all over the offense. He's an offensive genius. Overlooking this fact is ommitance for the sake of convience.
3. Saying that Marty is good because of past successes is a weaker claim. Plenty of formerly successful coaches and players flame out because of old age, or an inability to adapt. I think Marty hasn't necessarily adapted to the new era very well and at times it REALLY shows.
4. With Marty(and Trestman) we have had some significant scheming issues. His playcalling is undoubtedly predictable at times.
I personally don't blame Marty 100% for the offense, but he holds his share of the blame without a doubt. I think blaming him for everything is foolish, but absolving him from any blame for the above reasons is just not valid. When your offense is this bad there's more than just one reason, and inconsistent at best, bad playcalling at worst is certainly a factor. How big of a factor remains to be seen