Ok, you have my interest piqued.

I will readily admit that follow lists is all I am really familiar with from legacy platforms. Maybe I just don't know any better because of that. I am just not understanding how you could replace follow lists with relays.

Sure, you can have a relay that only certain npubs are whitelisted to be able to post to, but you'll still only see posts from them on that relay if they add it to their write relays. That is unless you have the relay aggregate their notes from other public relays... And then have the ability to qyery your relay for a subset of the notes you want to see...

Doable, I suppose, but it's a big ask for most folks to run and manage their own relay without them being made WAY more user friendly.