I didn’t know dead eye was a thing in RDR2 until about halfway into the main story when I accidentally activated it. If it is featured in a tutorial mission I must have missed it.
It suddenly made a lot of the missions, especially the ones where you need to shoot people riding on horses while you are yourself riding on a horse or train, much much easier.
You are making the mistake of conflating game quality with profit. He did not lessen the profitability of the games, on the contrary, and that is what the board cares about, not the quality of games.