The injuries are not limited to QB. I have never seen a team have so many injuries in general across the board, especially on the offensive side of the ball. They routinely work through 3-5 running backs each year. Kittle has been on and off IR his whole career. Deebo is like 1/4 for playing an entire season. I used to think bad luck, but I am becoming more convinced it has something to do with the scheme they like to run or Shanahan's offensive philosophy etc.
While I do think the OL does need some work in the offseason, and while Shannahan’s schemes have really helped Purdy transition into the bright rookie star that he now is, his schemes were what got both his QBs killed today. This is the thing I have never liked about Shannahan - he always has to prove he’s the smartest guy in the room, and ends up proving otherwise in the process. I go back to the Super Bowl when he was the OC for the Falcons (literally right before he took the 49ers job) - he had the league’s best running game that season and all he had to do was run the damn ball all second half and the Falcons would have been Super Bowl champs. Instead, as he always does, he got cute - and it cost the Falcons everything.
There are times when Shannahan looks like a genius - but yesterday he failed his entire team.