Here is the one core aspect about open source. There are people who really want to open source code without expectations of money at all. Immaterial if users are corporate or not. Perhaps for love of the art, career building or even just prestige and so many myriad motivations. I respect their choice. And it's not a shitty arrangement from their p perspective at all.
Yes, of course there are people who really want to do those. But op was presenting their main point of view related to "the slow evaporation" part.
Like op, more and more people can't get past the idea of starting or contributing to FOSS is no longer worth their time, due to various reasons, such as: their free labor of love was turned into another corporate money making tool.