"no remote signing for mobile apps" -- isn't this Amber? (I mean sure you've got to get it from an 'out of band' app store, but it's there and it seems to work reasonably well)

"not understanding relays / initial relay set not working" -- As someone who's come on board this year, I've never personally had a huge problem with this... I feel like a combination of an initial set + discovery of peers' relays should bootstrap most users pretty well?

"Search and Content Discovery" -- sure, yeah, but this is kinda 'the nature of the beast' ... New users have to understand that there's not just "one" Nostr feed, like there's "one" Twitter algorithm, etc...