Specially harem anime, they are basically the fantasy of some weeb but either way anime almost always presents a very colorful and happy life, how can incels endure watching that shit? It's worse than seeing normies normal lives tbh. Even if the anime main character is a loser at one point or another he ends up with friends and girls wtf
You start off asking "how can incels watch anime?" and then you elaborate further and describe shitty anime lol
Try watching:
Death Note
Berserk
Code Geass
Full Metal Alchemist (both of them)
Kaiji
Attack on Titan
Jujutsu Kaisen
Kimetsu no Yaiba
HunterXHunter
Goblin Slayer
Yu Yu Hakusho is a good oldie
Etc
There are a lot of good ones that don't revolve around relationships, sex, or anything like that. They are very story driven and they aren't even remotely blue pilled.
Also I stopped watching harem anime years ago because after the black pill hit me they were no longer funny, I couldn't laugh at it anymore or enjoy the moments in those series because I finally accepted my place in reality. The entire time on some level I was telling myself deep down "one day this will be you". When I accepted the black pill and I started looking at everything under the black pill lens I could no longer enjoy it.
I use to read To Love Ru, watch the anime, found it funny, etc. After the black pill it was just depressing.
I agree with you, I don't know how any incel can watch slice of life shit, romantic/relationship focused animes, ecchi anime (cocktease anime, waste of time, just go jerk off to hentai), etc. I can't stomach that shit anime.
I can only enjoy anime with all of these characteristics:
1. Protagonist focused storyline (male protagonist)
2. Little to no romantic theme
3. Deep lore that fleshes out the universe of that anime
4. Action and/or adventure themed
5. Minimal (very minimal) to no "nakama (friendship) power" boosts (really hate that shit, it's why Fairy Tail is 100% trash)
6. Protagonist isn't OP, he has to use his brain to win fights because most opponents are stronger than him