When I say "not relevant" I mean that probably freely shared paid contents don't affect small creator earnings too much, because they are often consumed by someone that casually find them, know about these "secondary" sites and is available to spent some time digging around.
I remember reading in a research that paradoxically sometimes pirated content helped to make famous and start/boost the sells for some small artists, ex. in the MP3 era.
An easy tool to sell content (paywall on nostr) and a fluent payment procedure (LN) can low the friction and increase the transactions volume; think about the MP3 situation: you can find everything online, but streaming services are booming, just because they offer a lot of value in a one click subscription, that remove all the UX pain.