I decided to give Mastodon another shot here recently, I found exactly one promising leftist instance, mastodon.lol. Bills itself as an "LGBT-friendly antifascist mastodon instance"

I watched another user get banned for saying that Azov were neonazis and I got banned for sticking up for them, then as part of his 240V power trip the admin posted a pity thread where he claimed we called him literally Hitler.

The only other leftist instance I saw welcomed all socialists except "authoritarians" so I assume it's either a socdem or sectarian anarchist instance.

TL;DR - Mastodon hasn't changed at all, it's still ran by power-tripping micro tyrants