It's easy to make what you want, it won't be Nostr-native, but it will use Nostr identities (keys) for accounts. Spam-attacks (friends requests) can still happen, but can rely on Web of Trust to filter out, giving a similar experience as Facebook/X. For what purpose though? Why not use Facebook instead? Building this, won't be decentralized in architecture, as you "can't" have decentralized and private at the same time. Could build it on Nostria, but I doubt there are any market for this (people willing to pay or revenue through advertisement with few users is worth little) and I would just be providing yet another service for free. What are your thoughts on the financial nature of such a social network?