I have yet to see a single problem with Lemmy over months of daily use. An instance may have crashed in that time but I didn’t notice not seeing certain instances when scrolling, and I don’t seek out particular communities. Helps that I’m hosted on a less popular instance, and the lemmy.ca admins seem to run a tight ship.
I block a couple of communities a day, but that seems to be expected. I also haven’t seen any kiddie porn.
Less discussion than Reddit, and less specific communities, but that’s been easy to forgive because well, fuck Reddit.
If an alternative pops up at some point, I’ll be sure to give it a try. Lemmy is doing just fine for me.