You're correct that many of those things have a lot of oxalic acid, but that domestication often reduces it -- but quite a few of our domesticated crops still have a large amount. We haven't gotten rid of it! The spinach, brassica, and carrot families are high in oxalic acid and/or oxalates, as are a bunch of fruits. And rhubarb is absolutely loaded with it, of course. All things to avoid if you have a family or personal history of kidney stones...

The other big toxins that come to mind are cyanogenic glycosides, lectins (improperly cooked kidney beans can kill!), and phytic acid. Those are well represented across a huge number of domesticated crops. But again, we use cooking and/or moderated consumption to deal with it.