Thor being fat and washed up doesn't bother me at all. It's really just an extreme result of his failure... or maybe the better word is "exaggerated". This may seem weird at first, but I'd argue that an important part of Endgame was to provide closure to all original Avenger characters (i.e. the main ones that didn't get dusted). For example, after Thor quite lost so much in his life (his family, his home, and most of his people) and failed to stop Thanos, he got a chance to talk to his mom and clear things up.
Thor wasn't the only character that received this treatment. Tony Stark went from being a person that only cared about himself in Iron Man to gradually becoming someone who learned to face his own fears and insecurities, and eventually become someone who truly thinks of others. (Although, I think Marvel screwed up
a lot of this over the years by focusing solely on Stark's insecurities and ignoring the qualities that made him so endearing to fans.) Tony's arc finished by him... essentially having a family and saving his surrogate son, Peter Parker.
Black Widow got her own absolvement by sacrificing herself. One common thing mentioned in previous movies was her having "red in [her] ledger". Also, in her mind, Clint is the only reason that she's alive... especially given that he was sent to kill her and he chose to let her live instead. So, her sacrifice was a means to pay back Clint, help everyone else, and arguably, clear the ledger of her past misdeeds.
Captain America also got a chance to finally move on. Ever since he was frozen for years, he has never really been able to... well... as the movie says, live. One common thing pushed in his movies is that Captain America doesn't do much outside of work... and his bromance with Bucky.
The closest Rogers ever got to having a life was with Sharon Carter, but that never really went anywhere in the movies. I guess you could say the phrase "his watch is over" sort of fit as we ended up seeing an older Rogers revealing that he finally got a chance to live the life he always wanted and missed out on before. He finally got that dance!
The only character that didn't get much was The Hulk, but I guess you could say the whole "Gray Hulk" thing was sort of his simplistic end. It was a basic way, which was literally told to the audience, of Banner to accept the Hulk and for the two to work together for once. Maybe Hulk didn't get much because outside of Thunderbolt Ross, Marvel mostly ignores The Incredibly Hulk as part of the MCU. It would've been kind of interesting if they would've brought Liv Tyler (Betty Ross) back for this movie.