As far as I am concerned they use Google Ads for advertisement, so, if you want to blame someone, blame Google Ads. I don't think coinmarketcap wastes it's time verifing all the ads that display on their website.
You are right. I didn't see any privately sponsored ads there. All ads are from google. There is no fault of CMC. Moreover, google place ads as per client's previous history. However, you can blame Google here.
This, It's not something that you can really blame them for. Are we going to boycott Youtube too? Best solution is just downloading adblocker. CMC DOES do some shady stuff, but this isn't one of them. Take for instance the fact that CMC switched to ETH as a price comparison when BTC was at all time low dominance, or that when prices in South Korea for bitcoin were hitting 30k and the prices were excluded from CMC.