definitely key rotation/revocation is something we need to work on (I think is the last thing core to the protocol that is still kinda unresolved)
but that's unrelated to this; if an external signer is too hard for a user, key revocation is going to 1000000x harder.
Installing an extension is not hard, if anything, non-technical users tend to end up with a million shitty extensions they don't need; it could literally be a click away in most browsers
the current state of affairs is that even a simple warnings saying "install extension X, if you just paste your nsec here you might get rekt" even just that would be orders of magnitude better
(sorry for the rant, I could not sleep on the plane and I'm super tired 😂)