For me, most of the mods I use are little quality of life things. I like to get mods that improve inventory handling, for instance.
Kind of a funny (but not really funny) mod story is that I realized as I was getting ready to play Megaquarium for the first time that it had Steam Workshop support. I wasn't too excited to start yet another tutorial, so I wasted time by looking through the mods. I found one that seemed interesting, that added new items for the gift shop, and subscribed to it, but I didn't activate it when I finally started the game.
Well, I played about 5 campaigns before I realized that the game automatically activates any mods that you subscribe to and that I had been using that mod the whole time. I had been thinking that the economy was a little easy, but hadn't realized that I had a bunch of things to sell that actually weren't in the vanilla game.