If someone published something as MIT and doesn't like it being used for LLM training, yeah that person can only blame themselves.
For GPL, it all depends if you consider a LLM "derivative software" of the GPL code it was trained on. It's fair to have an opinion on that either way, but I don't think it's fair to treat that opinion as the obvious truth. The same applies to art, a lot of it is visible on the Internet but that doesn't make it "a gift".