Ads are horrible and always ruins the experience severely, since there are never enough ads on a page for the producer to be happy.
I’m not against being a subscriber but I only do that for services that are extreamly useful, like search and email.
The point of Lemmy as a federated platform is that the cost is shared between many people. If hundreds of instance admins pay 10 dollars per month, it’s easily manageable. But if one instance becomes huge and needs to pay 10000 dollars per month, there is an issue for that instance, not the Lemmy network.