The thing people dislike, I think, is that actually implementing generics and handling all the syntactical and compilation edge cases is complicated and ugly.
But generics as a high-level concept are wonderfully simple and useful ("let me use different types with certain code constructs without having to manually duplicate them, and stop me from doing anything that doesn't make sense"). It would be a far easier call for languages to add them if they were just a bit of syntactic sugar instead of a whole new section in the manual. (I do think adding generics was a good call; practicality trumps a fussily clean design, in my book.)
But generics as a high-level concept are wonderfully simple and useful ("let me use different types with certain code constructs without having to manually duplicate them, and stop me from doing anything that doesn't make sense"). It would be a far easier call for languages to add them if they were just a bit of syntactic sugar instead of a whole new section in the manual. (I do think adding generics was a good call; practicality trumps a fussily clean design, in my book.)