People made GZDoom-based games with practically no programming skills above a bit of scripting. I’m not sure which of the existing games it was, maybe Hands of Necromancy 1, maybe something else, and users complained about slowdowns, input or something and one of the team members pretty much admitted as much.
Also when Doom modders graduate to make a full game and they know nothing else, just using GZDoom and the existing toolchain is just easy to use. Using GZDoom and thereby needing to comply with its open source license means that they cannot release the games on consoles. That means less chance to recuperate costs. Doubtful most would let that slip just for bragging rights.