> it's not unreasonable until you realize that Valve offers no other method for audiences that may be stuck with older machines to play the games that they purchased, which at the time of purchase they had completely met all of the system requirements.

They do - update to windows 10, for free, or install Ubuntu.

> A basic game should not have a set of rolling requirements that are ever-increasing.

They don't, but the platform that delivers those games can.