What do you mean by authentication? Most traffic on nostr is not even authenticated. Because everything is signed there is almost no need for authentication.
the nostr protocol is very basic. nostr consists of authentication and sending data to and receiving data from decentralized servers.
when you think about how most of the apps on your phone function, you'll realize that at their basic levels, they just authenticate a user and send data to and receive data from a central server.
the Other Stuff part of the N*OS*TR acronym lives here.
should everything be rebuilt upon nostr? no, probably not. could a large portion of the top 100 apps on your favorite app store be rebuilt with nostr in mind? absolutely.
eventually, we'll reach a critical mass point where developers and entities will want to do this, because when they do, they'll automatically have millions of potential users for their brand new application. this is powerful.
what's one application that you can't live without? could it be rebuilt on nostr? if so, are you willing to pay for it? have you submitted a bounty for it yet over at https://nostrbounties.com ?