ZDoom

It's not that easy. Many of the "high" settings would fall squarely into the "user preference" category, because many simply do not like them. That's why most of the advanced effects are disabled by default. In addition, the engine is still CPU bound in a lot of areas, and for most of that code there is no way to make it faster.

I have a really simple idea that isn't anything new.

Graphic setting presets,
A way to turn all the graphics to high, medium, or low for toasters.

this way someone who doesn't understand all the features in gzdoom and what they do or mean especially when they don't have explanations for them written down or easily accessible or understandable, and believe me this thing has a lot of them, can make gzdoom toaster friendly.