So #fediverse / #mastodon / #activitypub people, what do we have by now that is a usable alternative to facebooks group- & event feature?

I have a number of friends who work in event-related contexts, play in bands, do art exhibitions etc. most of them are still at metas platforms for basically 1-2 reasons. Twatter doesn't really matter at all to them because no feature keeps them there.

The Main reason for most of them to stay with meta is to promote their events & the easiness to invite people to an event or self-subscribe.

The other reasons are groups/channels where people have sub-discussion threads, that "feel a little bit isolated from the rest of the platform".
I'm not 100% convinced, that this can/can't be substituted by something like "only display this toot to people following the #hashtag" or something similar.

Reason number three is network effect at the end of the day, which is not really technically addressable from "our side" imho. Being able to show easy to use alternatives should be doable tho.