Messages in groups are not E2E encrypted, especially in public groups where anyone can read them even without joining. However, anyone can report the message to moderators. The public groups are often limited (temporarily removed from search, temporarily or permanently banned) if they do too much violations.
> However, anyone can report the message to moderators.
Good luck with that. And that's a seriously big issue. Moderators (and "moderators" in Telegram mean an alleged team of people they hire to moderate all content in Telegram - if you report content, the group administrators won't even be notified about that so they can act by themselves first) in most cases won't do absolutely anything.
