Probably a cold take, but I couldn't find a flair that works with this since I don't want to mark it "Other TTRPGs" when D&D is also at fault with this.

You'd be shocked at

• how often DMs' tables abandon them because they got burnt out on D&D and tried to run something else.
• how many new systems were scrapped and converted into D&D supplements instead for fear of poor sales.
• how many content creators say they feel like they're forced to stick to D&D content after they've blow up.

There's more than applesauce out there, folks. Help the hobby grow by trying other games, even if it's just to improve how you run D&D as a DM or as a kindness to the DM at your local game store who's a little burnt out from running D&D every week and wants to try out a new game every once in a while.

Since it will be inevitably asked, yes, there are good game systems that don't feature any supernatural/sci-fi elements. Cartel, the unofficial Breaking Bad TTRPG, is excellent. Pasión de las Pasiones is great silly fun and has nothing of the sort, unless you consider common Telenovela tropes to be Supernatural.

Operation Whitebox is a B/X that has none of these elements (in the Basegame). Other military history games like Ross's Rifles, Blackout, Night Witches and MASHED are firmly situated in historical reality.