To say that Goff only had 4 bad games from a statistical stand point would be correct. But, a QB can have good statics and even win a game and the coach may still fill feel the QB had a bad game. For example, if the QB misses reads, doesn't go through his progressions, fails to use his eyes to move defenders, has poor footwork, dumps a ball off to an outlet rather than hitting an open receiver deep, throws the ball away when a receiver is open, takes a sack because he is not reading the defense, making too many unforced turnovers or calls poor audible at the line. Goff should have looked better all year even in the wins. Better performance by the QB would have resulted in wins by a greater margin, fewer inconsistent games and wins not dependent on the defense having to stop the other team on the last series..
If the QB is not performing how the coach wants then that is an issue and clearly that is the case here. How good the Rams will be will depend on how well Stafford performs. I suspect better than Goff in most if not all areas. I like Goff, pulled for him from the start but even in wins he was underperforming. The success of an offensive scheme is dependent on MAXMIZING each play and to do so requires the QB to be on board and capable of doing what the coach wants. Offensive line needs upgraded and they could use some receivers who can do things the current group cannot. They could use a receiver with some size who can go get the ball and someone to take the top off. With those upgrades and a QB with Stafford's talent and experience and I see a frightening offense to go with what we all hope is a top tier defense next year.