Most games are slop of any genre. I think that NTR trends closer to slop more often though. Now I'm an NTR hater, I'll usually only play it if it's avoidable, FMC or I really like the artwork. Still, outside of some of the more established circles (not you Atelier Sakura, you're a slop circle) a lot of it comes across like it was written by a 12 year old hopped up on Mountain Dew and meme culture. Don't get me wrong, it's hot a lot of the time, but it still comes across as poorly written slop. Relatively well written vanilla/incest/harem is a lot less difficult to find imo.