I believe this is downstream of the domain name paradigm. We cannot get around the fact that our current system is set up with this user@domainname.tld system, not just for email but all sorts of protocols. User access and system login came before user-to-user-communication. Email is just the one protocol of which people think first when considering the "at" symbol. My point is @ is already very multi-use and is intuitive.
Discussion
You are right, the 'at' paradigm is present elsewhere, and it is always connected to the fact that the user is included, with his data, in that domain.tld system.
But Nostr is decentralized, the user identity and data are disconnected from the NIP-05 domain, this is just a proxy to the npub and some additional informations. Actually, I can have more NIP-05 too.
I don't know, I understand we are exiting a comfort zone, but I think it's worth thinking about now.
Right, we are trying to bridge from a user-domain paradigm to a un-domained key-pair paradigm. I don't know if a third way exists and would make for a reasonable and useful bridge.
NIP-05 is really just human readable pseudonym for an npub, by definition. I don't see a way to shorten or make human readable an npub without pseudonymization, so if already pseudonymous, what system would be more intuitive?