For me the biggest hurdle was finding apps that felt the same as the ones I was used to.
Take Mastodon: I've gotten used to Moshidon now, but previously I used Ivory, which is ridiculously polished by comparison. The natures of iOS and Android mean that there are very few Android apps that are as ...pretty... as most iOS counterparts.
Also; functionality. I guess because iOS users are more likely to pay for apps, developers are more likely to cram in as many features and polish as they can. If you try to replace an app with 1:1 feature parity, you're mostly going to be disappointed. Photos on iOS is an incredibly useful, user friendly app which has almost all of the library and editing features most people need. Immich comes close, but not quite close enough for me to be able to confidently say that you could switch from one to the other without really noticing.