I also think instances just need to have more sane urls. It sounds silly but like it or not branding does matter. Instances like beehaw and sh.itjust.works just rub me the wrong way during first impressions. Even some of my friends who I've tried to introduce to Lemmy are just like..."what the fuck kinda website are you making me go to?" I am not surprised that lemmy.world is big, partly because the URL actually sounds official.
We also need super-communities that pull in content from multiple communities/instances, better multi-instance search, and a way to migrate between instances before the masses will be okay with smaller instances.
It makes sense that general purpose instances would have the most users. I'm not a programmer so while I could still register there why would I pick programmer.dev?
The bigger issue I had in picking an instance was just in understanding the differences. I think it would help if instances advertised their stance on defederation, moderation, etc... to help people make a decision (or even to see that lemmy.world may be more similar to some other instances than they might think).
multiple accounts, one macro, one micro, works wonders. i like my lemm.ee account more but lemmy.world was my gateway as it was the one advertised to me
Would also be cool to have like a short questionnaire, like picking your class in Morrowind, but instead you end up on a German industrial metal music instance.