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
It's incredibly easy, and I don't know why people don't just run their own and not deal with petty tyrants on these big instances. If you have $5/month (or less, in some places) plus $10/year for an offensive domain name, you can be your own tyrant and put your hyperindividualized ideological prism over the flow of terrible posts.
For a one-time fee of like $50 you can run a tiny Pleroma instance on a Raspberry Pi.