Mastodon ends up creating significant echo chambers where admins ban communication with other instances for having people with different opinions to them (rather than just delisting in the public feed) and on can ban you and stop you moving your data to another instance.
On Mastodon, admins can also be pressured into banning users by other admins under fear of having their instances blocked, and admins are usually political activists.
I've avoided BlueSky because people are allowed to boast and defend being attracted to kids or spam death threats (including addresses attached), but not have differing political opinions, even when they're arguably mainstream.