Now I’m actually curious about how things would work in your perfect world.

The current gaming industry in the late stages, so it might be more productive to discuss the mid 2000s.

The vast majority of platform exclusives were made by studios/publishers owned by the platform. Exclusives were in turn a very big part of the value proposition of consoles, causing people to buy them in the first place.

If that had been outlawed by then, who would have produced the iconic games of each platform?