In addition to the more important issues that fedi-tips discusses I find their stance on anti-vax and US-election conspiracy theories... unappealing, which you can see being discussed here: https://lemmy.ml/post/143057
And that they haven't been shy about exerting their power for political purposes. The hardcoded slur-filter was explicitly about discouraging "right wingers" (I put that in quotes because I suspect their definition of right wing and mine differ), and they at least use to be open about their intentions to moderate the instances that they run as explicitly "left wing" (though I don't see a reference to that on the current site).