I've always really loved how Geto's trauma has been portrayed. His weight loss is a small detail that I love even though it's sad and besides that his messy, unruly hair (even in scenes where he had his hair tied in a bun it still looked unkempt) and the way he didn't even wear his uniform properly anymore... :( These little details make his story so sad; he didn't have the motivation anymore to do even the simplest of things. This is something that is very important to show when you're portraying depression and trauma in media and Gege (and Mappa) did it perfectly.
For anime onlys this episode was really important. All they know about Geto is from the movie where he was an antagonist and it's important for them to know what exactly happened that made Geto become like that.
Geto was empathetic, kind, caring, and loving. But he's the one who suffered the most from being a jujutsu sorcerer. First of all, his cursed technique is the hardest both mentally and physically. It's literally described as “the taste of a cursed spirit no one knows... Like swallowing whole a cloth that was used to wipe up vomit”. Consuming people's negative emotions daily? It's understandable why Geto felt so shitty after doing it.
But after seeing people cheering at Riko's death, seeing his friends die protecting non-sorcerers, seeing a whole village of more than a hundred residents call on for the death of two little girls, it's very understandable why Geto just snapped. He undertook so much burden and pain, so much suffering and hardship, and all it resulted in was humans mistreating sorcerer's in such a horrible way.
That's when this quote comes: “it's just that in a world like this, I couldn't laugh from the bottom of my heart”. He couldn't live in a world where he and other jujutsu sorcerers were treated in such a way. And that's how he started away from his ideals.
I really hope I don't have to see anime onlys blindly hate on him anymore now that his full story and trauma is in front of them.
Geto Suguru I love and appreciate you so much :(