Yeah it's hard to beat actual racism, especially when it's reversionary racism, like, they had to go back to basically 1E to dig up that racism - the 2E descriptions even are less racist, albeit not by much (let alone 3E and 4E), which is quite a thing.
If we exclude that on the basis it was so bad WotC took it out of print, then the field opens up considerably. I'd personally go with Spelljammer which just really manages to hit a huge number of bad points:
1) Overpriced and underproviding. Significantly more money, for significantly fewer pages, systems, writing and so on.
2) At the risk of being the "The food is awful and such small portions!" guy (which is, I'm sorry, a legit position - you can fail on both quality and quantity), the systems, lore, and so on that that they did provide were pretty low-quality.
3) Managed to basically screw over Dark Sun for no good reason whatsoever. Like, if you're not going to update it enough to remove the (significant) racist elements of the 2E version (largely elided in the 4E one, but only elided, not removed), fine, but don't half-arsedly set it on fire and then panic and put out the fire and say "Oh no, it wasn't Dark Sun we were burning, it was Dim Sol, totally different setting!". I'd honestly have respected burning down Dark Sun a lot more.
4) Managed to put monkey-people in without even thinking "Oh, this might get racist, let's be careful!", the most obvious red flag in the world, and of course, it got racist, on multiple points.
5) It's also just really lame and trite and twee, even by Spelljammer standards. It was always a setting in desperate danger of being twee, and this version absolutely triple-downed on the twee-est elements possible.
