So many. And the answer to all “why nots?”. Time. It’s time. So off the top of my head
Eat the Reich - “The year is 1943. You are a team of crack vampire commandos with one mission: drink all of Hitler’s blood”
Conan 2d20
Legend of the Five rings (5e)
Stoneburner - Deep Rock Galactic the TTRPG
Vaesen - Call of Cthulhu but rooted in nordic mythology
Heart the City Beneath - an award-winning complete tabletop roleplaying game about delving into a nightmare undercity that will give you everything you’ve ever dreamed of – or kill you in the process.
Shawn Tomkin’s Ironsworn series. Delve I regularly use for setting up point crawls. Ironsworn/Starforged/Sundered Isles have great collections of random tables, I use the book thematically most fitting for the situation at hand. The core tables of Action, Theme, Descriptor and Focus all get heavy use.
Kevin Crawford’s [SOMETHING] Without Number series have awesome tables as well. These however get more use when I need more detail. Prep stuff. Again most thematic book is picked first but I do have used Cites (cyberpunk) for fantasy cities.
When I want to create background for “medieval fantasy” characters I pick up Burning Wheel and burn something up. Through that I get a good selection of relevant skills to sue (for flavor)
Anything related to cosmos and mythology I say HELLO! to my growing collection of Glorantha material. From cult books to magic tomes and Atlases.