And my point is that such a system is unsustainable, due to asymmetry of work.

Lets start with a few things that we can know are true:

1. In any system of patrons and artists, an artist will have more patrons than a patron has artists, or the system is unsustainable.

2. I could create a competitor to Brave, "Fearful", tomorrow. So could anyone else.

As a creator, its possible that every single patron of mine will pay me through a different service, I then need to register myself in all of them, and either manually, or via a middleman, convert the disparate currencies to my preferred one. But, because there are so many different payment methods, its likely that the long tail isn't worth my time to receive payment from. Systems that accept payment on behalf of someone else and require work on the part of that party to receive the payment create this loss.

On the other hand, even if every creator has their own payment platform, there's no loss. Patrons simply don't pay the long tail of the creators that they use, and instead only make payments to the ones they appreciate the most.

iow, asymmetry means that creator-focused services are the only ones that can be successful except for very niche groups. So, if your goal is to support blockchain tech, Brave is great. If on the other hand, your goal is to get paid by patrons, its not.