What does your site provide - does it sell any products or services or is it purely ad supported? If it’s ad supported and you don’t care about your brand I’d say there’s no risk in switching to shittier ads, but if you want to keep a quality brand or have other services you sell, be careful as shitty ads could put off potential paying customers making it not worth it in the long-term.

The advantage of Carbon (or any other quality ad network like The Deck) is that the ads don’t really look like ads, so you can use them pretty much anywhere without degrading the UX and getting essentially free money. It might be not much but it’s still free money in exchange for a minimal change in the UX. Nasty ads might pay more but would degrade the experience so much I would no longer consider it “free” money no matter how much they’re paying.