I don't think its a question if him being the best for Lamar. But I don't think anybody thinks Lamar is a one-size-fits-all QB for an OC.
From a 30,000 foot view, my suspicion of the "we have to get Lamar a different OC" stance is that it's coming from a position where I don't think people care about winning football games. If that's not the objective, I think your objectives suck, and they should be ignored. I'm not saying everybody feels this way, but its pretty clear from that group of outraged people that the sole purpose of getting rid of Roman is to bring in a guy who will let Lamar throw it 40-45 times a game, almost purely to "prove" to fans of other teams that Lamar isn't just a RB.
I think deep down, regardless of whether people want to admit it or not, they just want to win the argument, more than actually winning games. I think there would be plenty of very happy people if Lamar threw for 5,000 yards and the Ravens went 10-7 and lost in the first round of the playoffs.
I want an OC who will maximize what Lamar does best. He's the franchise. He's the only part of the team you can't win without. Literally everybody else is interchangeable in some aspect or another. And what Lamar does best, pretty clearly, is being a dual-threat QB who teams can't pigeon hole into a running or throwing QB.
I couldn't give two shits less whether stud FA WRs want to play here, whether or not WRs can ever have 1,500 yard seasons in this offense, etc. Never cared about it once. I care about an offense that maximizes what Lamar's good at, and most importantly, an offense that will win us games.
And right now, I think its hard to argue Roman hasn't done a good job with either.