First of all we never went 0-16 under Billick so thats an irrelevant hypothetical scenario, we finished 2nd, 3rd, 1st and 4th, we made it to the divisional playoffs one year before going 5-11 when McNair fell off a cliff, thats when Billick was fired. The point is that we are not holding Harbaugh to the same standard that we held Billick, after almost a decade we are still inconsistent, Harbaugh still gets outcoached, adjusts poorly and gives way too many snaps to guys who have no buisiness being on an NFL field without covering their weaknesses.
Lets make this simple. I will list the Ravens records by year and you can see why the Ravens were a model of inconsistency under Billick while far more consistent under Harbs
2000: 12-4 SB
2001: 10-6 lose div round
2002: 7-9 no playoffs
2003: 10-6 lose WC
2004: 9-7 no playoffs
2005: 6-10 no playoffs
2006: 13-3 lost div round
2007: 5-11 no playoffs
Honestly the worst part of those records is that the Ravens cost themselves games by being undisciplined and should have been far better. It was not just that the Ravens were bad 3 of 4 years, its that the Ravens were pretty much not getting it done since 2001 other then 1 good year in 2006 which showed what could have been.
Now lets start the Harbs era (yes I am 100% avoiding spelling his full name on purpose)
2008: 10-6 lost conf champ
2009: 9-7 lost div round
2010: 12-4 lost div round
2011: 12-4 lost conf champ
2012: 10-6 SB
2013: 8-8 no playoffs
2014: 10-6 lost div round
2015: 5-11 no playoffs
2016: 8-8 no playoffs
Now 2015 was a weird year and I get that your opinion is basically "yes every good player got injured and it was a tough schedule but they still should have won and made the playoffs because reasons" but the thing I want you to look at is the consistency. With the Billick Ravens the record was all over the place. You had no idea what you had and no idea what would happen, but Harbs is able to get the most out of the roster he has and it shows by the fact that there are not random spikes and ebbs in the record. When a team has massive swings in there yearly record I have to wonder how well they are being coached especially when there is not a lot of talent turnover, however the Ravens only really took a 2-3 game drop off in record after a massive talent turnover after the SB and a bunch of signings that did not work out that really hurt the roster (Pitta, Rice, Monroe).
Right now the Ravens have a young talented core that if they could stop getting hurt all the time would be contending for SB titles. Obviously a few more OL will be nice but the team has a lot of talent at a lot of positions and are deep at those positions as evidenced by the fact that they are still competitive.