It's even worse than that: when you pay they now have your full legal name, payment information and home address. More than they likely had before you opted out of advertising!
My view: if users want to see mastodon content then they should go to mastodon. I say this as a mastodon user. Lemmy isn't an RSS and microblog reader, it's an entity all of its own and needs to evolve its own culture.
So that leaves two options then. Leave the front door wide open, don't bother with any locks. Or shut down the web site. I'm for at least closing the door with the right robots.txt
Is there a peertube instance that is live music recordings friendly?