Yea it's a very fair point. Simple key pairs is just the starting point. We'll need to figure out how to rekey people potentially with something like social recovery and/or pre-commitments. I believe we'll solve these problems over time though. Getting adoption for an interoperable protocol is much more challenging though imo and that's where Nostr is beginning to shine
My approach for theft would be to have key aliasing and reasonably secure hardware wallets. You'd have a 12 word seed you only ever enter into the hardware wallet so it can generate the signature you need to set up an alias pointing to another key. Once the alias is set, the seed is deleted from the hardware and you interface with nostr through the other key. If the everyday use key gets stolen, you change the alias.