I don't see public/private keys as a hurdle for Nostr adoption.
We often say that people buy bitcoin at the price they deserve. I think that same ethos applies to Nostr.
Using an extension is not hard, it's just different. Protecting a seed phrase is not hard, it's different.
Users who appreciate Nostr and see the vision will rise to the occasion.
There is not much rising to do, but I'll be nice.