Who were the EU democratically accountable to? If it isn't the UK electorate, then it isn't democratically accountable. That's the point. People don't like the idea of someone making laws whom they cannot remove. I can't see why someone has more trust in a beaurocrat in Brussels that they cannot elect or remove, than their own MP. I can't see why a Dutch, French, German, Maltese or Irish MEP is the adult in the room, when for some reason our own elected representative is the child in the room? If a UK government makes decisions on a hypothetical bill that I disagree with, and I voted against, I can console myself that a greater proportion of people in my town and by extension, country, wanted this person with these views. Its less palatable when I oppose it, our politicians oppose it, but people from another country want it so its imposed on us.
Would your view be different if the party in power in the UK were more aligned to you ideologically? Are they still the child in the room who need a grown up German or Spaniard holding their hand?
For what it is worth I was a remainer, now an accepter. My thoughts were that the treaties, directives, legislation etc. were so ingrained an integrated that Brexit wasn't worth the hassle. But the sovereignty argument is one I have great sympathy for.
All in all, Brexit is down to EU mission creep where a trade block snowballed into greater and greater degrees of federal political and legislative union. That is where many drew the line.