The "perceived" democratic deficit. People have bought into the line that the UK must humbly accede to every EU decree which pops into being from a host of faceless, undemocratic EU bureaucrats. This demonstrates an ignorance (willful or accidental) of the way in which the EU works and the UK's position within the EU.
As I've mentioned a few times recently, for decades successive UK governments have taken the line that EU successes are their successes but any unpopular measures should be blamed on the EU (whether true or not). It's also been the case that if the UK "only" gets 99% of what it wants then it has been bullied by that nasty lot in the EU, not that the UK has twisted arms to force the other countries to accept the UK position.
IMO it's political cowardice of the first water (and it's been exhibited by Labour and Conservatives) to engage in negotiations, agree an outcome, rubber stamp its implementation and then bleat about "EU interference" when it later turns out to be unpopular. The EU has been blamed for the ban on filament lightbulbs and energy inefficient vacuum cleaners as if the UK government had no hand it it whatsoever. The UK government IMO did the right thing, because more efficient alternatives were available they sought to get rid of the less efficient alternatives (the British public are very conservative so expecting them to switch for themselves is unreasonable). The public bleated and so the government blamed the EU instead of sticking by, and up for, their decision - political cowardice
Of course had the public not kicked up such a fuss then it would have been the UK Government helping to save the UK consumer money and help to protect the environment