It’s been invite-only for all five and a half years I’ve been there so I wouldn’t expect that to ever change. Fortunately it’s really easy to get an invite code. Just post in the official subreddit and the mods or another user will give you a code. It’s just enough of a minor roadblock that it helps filter out bad actors.

Personally I prefer Lemmy. But if you’re like OP and looking for conversation focused alternatives tildes is worth joining.