Avatar is mediocre, yes, but I don't agree with you on Avengers. In fact, much of the MCU in the previous decade was playful and entertaining, with good performances. I don't get too snobby about it. But on the other hand, the problem is too much of a good thing, with everyone and their cat trying to replicate that success (including Marvel themselves, still trying to keep the thing going when it really came to a natural end with Avengers Endgame). :)