Not a technical thing, but…
Better user interactions. I know not everyone came from reddit, but there are so many reddit-like interactions across Lemmy. I’m talking about not assuming good faith and jumping down people’s throats. Low-effort comments (I’m guilty of this, too). The need to always be right and continue arguing for no reason.
It was tiring to see this on reddit over the years. But it’s sad to see how much of that behavior has made its way to Lemmy.
With federation, however, there’s not really a good way to solve this, since each instance, including self-hosted instances, determines their own moderation and “culture.” But it would be something I’d like to see improved, even i we each have to do it ourselves.
On the technical side, absolutely mod tools. It’s stunning how bad they are here. And I’m coming from reddit, where tools were poor.