> I imagine it would be much more straightforward to port pretty much any indie games to consoles like Xbox original onwards, PS3 onwards, Wii onwards, maybe Windows 7 average desktop and notebooks (lots of indies already use older direct x and are compatible with windows 7 ,

Not a game developer, but given the lack of ports between current gen gaming systems I would assume that it is not straightforward. Sure, a game engine will magically pump out your game for different backends but even supporting Vulkan and Metal results in much gnawing and mashing of teeth (and a lack of games on Apple hardware).

Then there is the developer ergonomics. I know that I hate having to write code to maintain compatibility for even 5 year old standards. Each GPU and game engine is also a unique clusterfuck of incompatibility and subtle bugs that crash the shit out of games. If you want to support that old hardware, you will need to test on the actual hardware. Why bother with all that when there is no money in it and your team just wants to move on from a project that already took 5 years of their lives to develop?

Forward compatibility is something I strongly agree with but backwards compatibility is a logistical nightmare.