The ex-Warsaw pact (EU enlargement) countries should have got together into a separate 'club' and worked their way to prosperity before 'promotion' to the EU. They were not in the same league as us and we've "brain-drained" their best talented, hardest workers, leaving their at-home popultations even less likely to catch up with us, other than by milking EU net contributors, like us.
EU fed our resentment for it as an institution by sponging off us and taking the "oh, you can afford it, old chum" attitude.