I have yet to see anyone talk about UX improvements for new users

That's something I have written a lot about :) More with words it must be easy and retard friendly. Passwords difficulty reduce and mobile dapps that makes everything easier.

And I'm sure others did too :D

Id say that we remove all need for keys as a default. Just login through email and password. That way we compete in ease of use with legacy social media that people are familiar with.
Moving them into true Hive account use gradually.
That can be done through custodial services from frontends.

Means for me "Softwallet". That's something I have written about a lot too :) Simple Number Wallet and Number password and a frontend can connect it to email. Would also reduce the cost of onboarding to close to nothing chain-wise.