If you're asking if there's a version of D&D that's pure math and no roleplay, the closest thing I can imagine would be Dragon Dice, or something with the mechanics of a very basic roguelike. The math in D&D itself such as in combat is affected by your character's stats and the encounters created by the DM, so the mechanics and the role playing are kind of tied together.

I am also past the age of wanting to believe in magic. And also past the age of having time for long plays. Most of my friends are busy doing serious adult stuff.

So outside of baroque dnd-like systems, my personal favourite right now is a subgenre called journalling solo RPG, which are often minimalist, but covering all kinds of themes and topics.

If that's all you want, there are loads of combat games with miniatures. I've never played Warhammer, but that's obviously the biggest one; I've enjoyed the Star Wars X-wing combat game as well.