Love and use Nostr.build, even have a T-shirt from them. But to be clear it is a centralized service. Just good guys running an open sourced centralized service. At least that’s my understanding from their website where they describe using cloudflare and AWS. Please correct me more technical folks if I’m off base. 

 Everyone should use blossom now  

 Blossom has no nip, is glitchy and has not been catching on, so far 

 This is correct. The difference is people have choices, doesn’t have to be us.