Marketing is a fact of life, I think. Of course, there's good marketing (making people who might enjoy your product aware of it) and bad marketing (annoying people), but if you hope to reap the benefits of having your work in front of a lot of people, you do have to reach them.
What OP says, and you miss, is that some people are not interested in reaping benefits. They are interested in doing work.
They are constrained by time and money, so yes, sponsorship can help their projects, but they are not in it for the reaping. If anything they will be happy to see a lot of people reap benefits from their work, not the other way around.
How many are like that? I don’t know. Maybe not a lot, but some for sure.
There are tons of people who like to just go do stuff, and that's great! But if you don't promote it at all, certain avenues are not open to you.
I was more thinking about contributing to other projects. What incentive do I have for fixing an issue in someone elses repo?
With this sponsorship model, the benefits will only go to the dev whose name is on the repo.
It's going to be very hard to market yourself as the guy who fixes random issues in a bunch of unrelated projects.