Decentralization and censorship resistance are the fundamental qualities of Nostr and, indeed, all that the mandatory part of the protocol provides.
That is fundamentally more important than a payment or donation system. 

 the payment system is very important as it's familiarizing people with lightning 

 There are many things in the world. The purpose of Nostr isn't to familiarize people with any one of them.
I don't think it's important. 

 I think it's important that Bitcoin adoption happens as soon as possible 

 Many things are important, it doesn't mean everything has to be about it.