In addition to the recommendations for Powered by the Apocalypse games (specifically Monster of the Week) I'd also encourage you to look into the FATE system, especially FATE: Accelerated Edition[0] and its SRD [1]. It's designed to be fairly light on the mechanics, and to help the GM and the players focus on the development of a story within those mechanics. I've been running a homebrew-story FAE game with a group of 4 friends and I really like the flexibility it gives us to focus on the narrative and character development. Also it's designed to be a pretty minimal time commitment to learn the rules well enough to give it a try.

[0] https://www.evilhat.com/home/fae/

[1] https://fate-srd.com/fate-accelerated/get-started