TBH I don’t have strong opinion where the boundaries of FOSS are. But I can understand their will to minimize effort where you see it fits as an engineer. If they think they lack of manpower to do something, it’s their vision as they put work towards it. We can help if we like, agree, disagree or ignore. Does not make sense to blame them though, that was the point of my first comment.
I tried steam link for several games in last weeks and it seems that black screen issue exists in quite some of them. My case is Nvidia on Wayland and it seems to me that could be a culprit in my case. If it’s the case for you, too - try xorg first.
Sorry, can’t help you, but interested in solution, too.