I am not a prolific "poster", I am not hugely tech-minded, but I check in on nostr fairly regularly .. for what it's worth, here's what i think ..

Firstly, they're notes, not posts.

Secondly, your global feed (or search, if you will) contains a lot of spam, relay management fixes this.

Thirdly, there is no algorithm .. if you're not seeing many notes in 7 hours, then the people you're following are not noting 🤷🏻

And finally, curate your lists.

Hope this helps

🤙🏼