Customizable grid size on both the home screen and app drawer are the two biggest for me. Also being able to hide apps from the drawer while keeping them installed. Home screen gestures are a big one that I don't personally use anymore.

It boils down to preferences imho.

I like text-based stuff in general, so having a launcher that displays my favorites app as text and launches any app as soon as I type the beginning of its name is a real plus for me.

Open-source and de-gafamisation also matter to me, so I want to make sure knowing my launcher doesn't track me - I usually choose one that's available onF-Droid for this reason.

OLauncher has these features and has a smaller footprint than default launchers, sl I swapped.

But afaik there's nothing "wrong" with the AOSP launcher.