100% agree they were not good enough this year. Some really strange and frustrating things going on. They were really, by most counts, a pretty mediocre offense (FootballOutsiders- 10th, Pro Football Reference- 19th, ESPN's FPI- 17th, for example).
But I also don't see this as a wholesale changes sort of offseason for the offense. One, because of the lower salary cap and Goff's contract they're simply limited. And two, some smaller changes could add up. Personnel-wise, to me those changes are upgrading at center, finding a speed WR4 and finding a good blocking TE. You could argue those are pretty minor changes but I think they would equate to opening up the passing game more
and solidifying the running game even further. The Rams have found a really good RB in Akers. He could be a 1,300-yards guy in 2021 with those additions. And if you have that and the weapons the Rams have at WR and TE then you can do some good things.
I would also like to mention special teams here because one other thing that hurt the Rams offense I think was poor field position. They were 24th in average starting field position (1st in 2017, 5th in 2018). That plays into things too. Now that the Rams found a reliable kicker again and hopefully with a new (better) special teams coach things improve there.