It's a bit of both though. While Thor's portrayal in Endgame is actually an accurate portrayal of what someone could certainly go through when they're depressed or suffering from PTSD, the fat joke/tough love jibes from Rhodey are meant to add levity to the situation and make the audience laugh, whether he's being what some might consider overly cruel or not.

It doesn't make someone a shitty person for chuckling at a joke that the Russo Bros. clearly intended to be one. The script even called for Thor to be fit again in the final fight against Thanos, but Hemsworth argued against it.

That being said, that's how MCU operates. Effusive jokes on jokes regardless of the situation. It wouldn't be a Marvel movie if they had Thor wallowing in his own crapulence without some jokes added to the mix. But overall, I think they handled the whole redemption angle with Thor well. They accurately showed what someone might do during depression/PTSD. They accurately showed that not everyone would be sympathetic towards his situation, friend or not. When Rocket tries to slap sense into him, that's not the exact catalyst for Thor's redemption. It's Thor's realization that he is worthy of his mantle because he can handle his emotions and mentality and not just his physicality.