There is actually an algo! They are called “those who joined #nostr a while ago” If they do not follow you and repost your notes, you have 0 reach! To fix this issue, nostr devs should implement an open-source algo that we can use to be able to get our voices heard and spread to those who want to see it!

Lot's of algos exist now to be honest. None exist at the protocol level. However, many popular clients have trending notes or what's hot feeds, etc. and various DMS feeds. Content discovery is getting better.