By that reasoning, VorpX should be illegal. Even the PiTool software should be illegal, as it modifies the behavior of games, for instance to enable fixed foveated rendering where it wasn’t implemented by the original developers.
I understand that people would love that everything in life was free. For example, I would certainly like to get new tires for my car for free, instead of having to pay for them. Or an aftermarket exhaust system, or a new coat of paint. Since I already paid for the car, the rest should be free, right?
However, that desire doesn’t entitle you to make random accusations. There is nothing in my mods that exploits code that doesn’t belong to me or is not properly licensed for use.
There are two types of mods. One type takes the assets, or game design, or ideas, or any other sort of intellectual property belonging to a game, and transfers it to another medium. For instance, the mod that allows you to play Bioshock in VR on the Half-Life: Alyx platform. Those mods need to be authorized by the owners of the original IP, because they allow you to benefit from it without proper compensation to the original IP owners.
The other type is what I do, or VorpX does, or PiTool does: improving the experience offered by a game, without transferring the IP to another medium or platform, and without offering any way of benefiting from the IP that doesn’t require paying the original owners. In simpler words: if you want to play my Horizon: Zero Dawn VR mod, you have to buy the original game first. The original developers and publishers are properly compensated.
There is nothing illegal in that. Although there are two caveats: the owners of the original IP might feel that my mods (or again, VorpX, PiTool, GeForce Experience… anything that modifies the way the game looks) disparage the original IP, putting it in a bad light, and/or they might find that my conversions are in competition with a product that they want to release based on their IP. For example, if Rockstar came out with their own VR version of Red Dead Redemption 2. In that case, they would just need to ask and I would of course take down the mods or modify them in a way that stops the alleged damage to their IP.