A World without Exclusives?

There are certain constraints particularly unique to the video game medium that makes it impossible to create a future where multiple companies are producing multiple systems that all games must be capable of running on. Not only is there going to be quality issues between versions, but there's going to be novel control schemes that are not supported by certain platforms. For example, touch screens are not implemented on consoles but are in mobile games. Entirely different controls schemes would have to be implemented to support machines with no keyboards for certain genres, and this effort falls on the developer who needs to meet the demands of all markets. The comparison between certain industries mainly music and movies is a flawed analogy as technology to render and optimize a game for multiple distinct platforms--and the platforms must be distinct or otherwise there would be quite a few lawsuits--is much more complicated and takes more development time than the R&D of technology that has a simpler function in transcribing a single set of information, not deluge of possibilities that may take place when given player agency.

In a perfect world, microsoft and nintendo would stop making consoles and everyone would make games for PS5.

I don't think so. Mario kart would not work on any other system if it did it probably won't be the same