I have no idea how it may in practice be done badly, because I've never encountered it personally. But I suspect the reason people widely hate the concept is b

I have no idea how it may in practice be done badly, because I've never encountered it personally. But I suspect the reason people widely hate the concept is because schooling pounds into you that there is only one way to get the right answer, and it must be exact. And so when people complain about being tested on trivia, what they really mean is "I want to be tested on trivia that I know". I would actually like to be evaluated based on something other than knowing trivia, but of course I would not like to take a stupidly constructed test.