New user here! Is there any way or a website that shows new users joining and lemmy instances growing?

Those are instances that haven't enabled captchas yet and have been raided by bots. https://lemmyverse.net/ seems to exclude bot instances using its "smart sort" but it gives you only active users.

There have been a lot of junk bot accounts created, but those accounts aren't active (they don't post anything, thank goodness) so they will not appear in a measurement of active user accounts.