I think we need to separate the system from the product. With Reddit they’re the same, with a single owner. With Lemmy/ActivityPub, just like with email, there’s an underlying system that nobody owns. It’s an ecosystem of pieces created by lots of different people.
It is a good thing that people are building products on top of that. Some of them are FOSS and some of them not. As long as no-one gets too much control of the underlying system then that’s great! Users retain choice and can choose FOSS apps if they want, or they can choose something like Sync.
I agree it would be sad if the only apps were paid, but I think a mix is a sign of a healthy ecosystem.