While Schottenheimer is definitely a very uninspired hire I'm not really sure why he gets so much grief for his time in Seattle. I assume it's mostly because of how run-heavy they were and how the whole "let Russ cook" nonsense took hold in the discourse surrounding the team.
But look at these numbers when he was there:
2018 (10-6): Wilson had 35 TD's to just 7 INT's, 8.1 YPA and 65%+ completion. Chris Carson was their leading rusher averaging 4.7 YPC with 1100+ yards.
2019 (11-5): Wilson had 31 TD's to just 5 INT's, 8.0 YPA and 66% completion. Chris Carson was again their leading rusher averaging 4.4 YPC and 1200+ yards.
2020 (12-4): Wilson had 40 TD's to 13 INT's, 7.5 YPA and nearly 69% completion. Chris Carson was again their leading rusher, this time with only 681 yards but again averaging a strong 4.8 YPC.
That's 106 TD's to 25 INT's over 3 years with nearly 8 YPA and 66-67% completion.
Over the last 3 years Mahomes has thrown 116 TD's to 31 INT's with roughly 8 YPA and around 66-67% completion.
This was clearly the best 3 year stretch in Wilson's career, and for the majority of it he wasn't surrounded by much. A JAG in Chris Carson at RB, one of the worst OL's in the league, and a good but not great WR in Lockett as his lead guy in 2018 and 2019 before Metcalf emerged.
Metcalf was a rookie in 2019 and started to blossom into a star in 2020 but that was Schottenheimer's last year. Of course they went 12-4 that year and Wilson had arguably the best season of his career, but they sputtered against the Rams in the playoffs largely because of their OL and that was the final straw.
What's also interesting is that in 2018 they were much more run-heavy with Wilson only averaging about 27 attempts per game but that increased in 2019 and then again dramatically in 2020 once Metcalf started to come into his own, with Wilson averaging 34 attempts per game. So clearly he's fine leaning more into the passing game if the talent dictates it.
And of course we've seen what's happened to Wilson and the Seahawks since. In 2021 their offense took a significant step back under a McVay disciple, they went 7-10, he was traded and then obviously cratered in Denver. Their offense was solid this past year with Geno but with significantly better talent at RB (Walker) and along the OL than what Schottenheimer had from 2018-20.
And their defense was a thing of the past from 2018-20, an average at best group and certainly not able to function as the engine of a team.
Long story short, there wasn't a whole lot for Schottenheimer to work with in Seattle beyond Wilson and Lockett and yet the offense ended up performing mostly well, with it being probably the most individually productive stretch of Wilson's career.