The nice thing about federation is that you can always go somewhere else if you disagree with a particular instance.
Lemmy's devs have questionable politics at best. IMO, I don't care as long as it doesn't impact how they run the site - people have a right to their own opinions, as long as those opinions don't harass or hurt others directly.
But let's say they changed one day. Maybe one day they added something to the code forcing everyone to praise the CCP or else.
Because the software is open-source - people could fork it before the change. It's out there already. People can totally make their own little variants of Lemmy with added features, if that's something they wanted to do. You can modify the code yourself and then self-host the modified version. No matter what Lemmy's devs do... they have no power on your instance. A fork means you own the code.
I've seen the sentiment tossed around that it's unethical to use Lemmy because if you donate to the project (or contribute to donations towards the project) you are financing people who have bad politics. That's your prerogative. I personally disagree - again, as long as your politics aren't actively contributing to harassment/harm you shouldn't be punished for them - but I understand the sentiment.
To that, I say - well, there's other options. That's the beauty of the Fediverse - you don't have any Musk or Spez that comes along to ruin everything. I'm on Kbin, which I like a lot. The dev is a great guy, and I really like how it combines the best of Lemmy and Mastodon.
Even if you want to stay on Lemmy, there are wonderful communities on Lemmy that disagree with the direction of the devs. Beehaw is a great place with a fantastic mod team, for example. You can donate to Beehaw's devs and know it's going to keep Beehaw running, and it's not the same as supporting Lemmy directly.