If you don’t mind his particular style, the SsethTzeentach video is what convinced me to give it a fair shake. The in-game tutorial and tooltips are pretty good though, and will get you started. Overtime you’ll discover more and more systems. Oh and just so you know, the demo is the full game, but a version behind.
Have to throw CK3 out as my personal favorite grand strategy game (though EU4 and the like are other options). There’s nigh infinite content in weaving the story of your family and realm, and mods add a whole new layer to it.
Besides the obvious Minecraft recommendation, maybe Terraria, Satisfactory, and if you’re willing to allow it, something like Smite would be another good option for him to play with his friends.