I agree with most of yours as well, though I read a lot of articles from guys who watched closely his last season in San Fran that said he had showed considerable improvement in his ability to be more than a single read passer, and really suffered greatly from poor receivers that year. I agree he had a ton of weapons early in his career and a good defense for the most part (although like I noted, the D didn't do a lot of favors in the playoffs and he and the offense had to do a good bit of heavy lifting then...but I mean, better opponents so to be expected to a degree), but when that team exploded or imploded, however people want to define it, it went to shit really fast.
Frankly that team was so bad both him and Gabbert left town after that year, although Gabbert won an extra game or two, Kaep looked far more efficient by the numbers overall. Just hard to do much (either of them) when your D was giving up 30 points a game and their lead wideouts were nobodies. It's actually pretty crazy the turnover since that 2016 seasons in San Fran and you have to give Lynch and Shanahan a lot of credit for rebuilding the team on both sides of the ball so much the last 2+ years. Pisses me off to no end knowing Kittle was a 5th round pick while we're still paying forever hurt Jordan Reed like $10M a year.