Lemmy has a list of themes. I like most of them but some of them are weird like the notepad one(called sketch). But I think everyone either uses the dark or light theme. I am not requesting the team to remove all the themes, maybe some of them can be removed?
There’s already an easy way to do that, check the theming guide: https://join-lemmy.org/docs/en/client_development/theming.html