Gaming Ballistic is about to launch Mission X, a modern action slim down version (powered by GURPS). https://gamingballistic.com/2026/05/02/lets-get-this-started-again-mission-x-updates-coming-soon/
I use inkscape for overland maps. I use Watabou Medieval City generator for city maps. I use Dungeon Alchemist for dungeon/indoor battlemaps.
I took a page from Flee Mortals and use actions instead of spells for NPC combatants.https://shop.mcdmproductions.com/collections/flee-mortals-the-mcdm-monster-book
I think that main problem is lack of support for the former. Some people really like to do that, but rolling your own is hard. There are some third party supplement that might fit.
GURPS Celtic Myth, GURPS Arabian Nights, and GURPS Mars