I don’t see any problem with modders charging for their mods. They are doing work, and deserve to be compensated.
If they’re creating additional deep content, I can see that being worth paying. If it’s just some skins or configuration edits like wonky gravity, that would not be worth money to me. But I think it’s a good thing to be able to add micro transactions for.
Take the original DOTA for example. A warcraft 3 custom map. It eventually dominated the custom game lobby, at least 3:1. I would have no problem with the creator(s) making money off their creation that contributed a ton of replayability the game.
When it comes down to it, it should be the modder’s choice on if they want to charge for their work, and the consumers choice if they want to pay for it.
Also why I didn’t have problems with microtransactions for skins, particularly when it was community driven like DOTA 2. Artists can make money creating non-game altering content, and fans get to personalize their characters.