Well, yes. You can. All you need to do is find the .nsp file online and install it. It might need a user linked to a nintendo account, but the nintendo account does not need to have a Nintendo online subscription or even connect to the internet, aside from the initial linking process, I assume.
But really, you're probably better of just getting retroarch, the interface of the NES online is really nothing special and you're missing out on a ton of features by not choosing retroarch.