E.g. the nag problem would have been solved simply and effectively with something like do-not-track header (probably as OS setting, as apps are often even worse than websites with tracking). Also enforcement of obvious violations taking years and years, especially against large corporations, means it's just violated all the time.
EU also failed to give good interpretation guidelines early on, causing massive piles of overjealous lawyer CYA red tape and just silly stuff like removing names from apartment buzzers.