The solution outlined (give employed software devs $50/year (or month) to spend on any open source software) will have a problem in that the software devs know

The solution outlined (give employed software devs $50/year (or month) to spend on any open source software) will have a problem in that the software devs know about and want to give to itself has dependencies the devs may not know about and therefore not give to. There's a bit of distance between the open source software we know we use and the open source software we don't even know we use