id Software, Valve and 3D Realms included their SDKs on the disk. All the way back in the 90’s they gave players the same tools they used to build the game. Any game that descends from Doom, all the way into the Source engine, store their assets in .wad files.

Those were not the first modded games.

In any case, you’ve already made it clear that you disagree. That’s fine, but it doesn’t make your view the only valid one.