Stafford adjusts to pressure better, has a stronger and more accurate arm, makes more off schedule plays, does not lock onto his primary target, and sees the entire field. Goff was only looking for close, shorter throws. McVay even said in one post game press conference that our QB needs to see the field better. If you watched much of the All22 you can see receivers coming open for the Rams and never getting a look from Goff all season.
I also know that many of us considered rollouts as a way to mask the offensive line woes. They are also used to give QBs less field to have to scan. They were about McVay trying to simplify things for Goff.