Indie developers, like the 1-5 staff game studios on Steam, never stopped doing so. You can run most indie games on an old PC today. The big AAA game companies like Activision are taking a big gamble on the next generation, which they insist you'll need a newer console or PC to run. Bethesda tried that with Starfield and it didn't work out so well. The game's not as terrible as people say, but its kind of in the middle of the pack of AAA gaming RPGs and it demanded a fairly large amount of VRAM to run well. I predict things will not go well for games like Modern Warfare 4 that won't run on the last gen consoles or PCs. If developers aren't aiming at older devices then they're making a niche product not a mass market product