Honestly, I wouldn't even play a game where paying for power-ups was the norm. It's not something I'm interested in.
Skins, on the other hand... so, to start with, I play FF14, which has a cash shop for things like special outfits and emotes. While I wouldn't dump all my disposable income into cosmetic stuff, and I sure as hell don't trawl the cash shop looking for stuff to buy, I'll buy stuff here and there if it really catches my eye or if it could be useful. For example, I went to an in-game wedding over the weekend, and I didn't have anything to wear that was really appropriate, so I hopped on the cash shop, looked at a couple of dresses, asked my friends for advice on which one looks better, and bought exactly one outfit. And then there was when I was first setting up by subscription after my free month ran out, and I stumbled on a set of emotes inspired by one of my favorite television franchises of all time. Those were the only things I bought from the cash shop... though I have to admit I'm tempted to buy the new cat ear hood (which was heavily advertised when it came out) just because cat ears are kind of my thing.
So I'm definitely not in the "buy all the skins" camp, but I'm fine with buying a couple of items here and there that enhance my enjoyment of the game. And, of course, this leads into why lootboxes are evil. In a game that uses lootboxes, you can't just buy one or two cool things. You have to keep buying lootboxes and opening them again and again and again and again until you get the thing you're looking for. It's exploitative, and it trains the mind to derive enjoyment from addictive behaviors.