[1] Not saying over-regulation isn't a problem, merely not my main concern.
I find it somewhat insulting I even have to argue for this - this move of power further away is a change. It should be justified, instead of happening by default, while the former status quo of sovereign nations has to argue for its continued existence.
However, if you believe this, you must equally believe that growing a single nation's population from 10M to 500M has the exact same problems. So if you were from Belgium and it grew to 500M, you'd have to support a move to partition Belgium into 50 separate nations, for the same reason you're against the EU. Right?
Such as how the British empire partitioned into the US, Canada, Australia.., or how China and Japan became distinct countries despite a common origin? Yes. A shared identity can support a larger country (the inverse can be seen in the breakup of Yugoslavia), but not without limit.
> I buy that smaller democracies could work better in many ways
It's not just about size. It's about the simple and intuitively obvious idea that it matters who chooses your rulers. I find it both fascinating and frightening that people have been so trained into ignoring their instincts (evolved through millions of years of inter-group competition, but now casually dismissed as "irrational"), that this basic notion now needs arguing.
[1] A small correction: I am not against the EU - the opposite, I am strongly in favor of it, for the simple pragmatic reasons that it safeguards peace among the member states, and because the relatively small European countries would otherwise be picked off individually by larger geopolitical rivals. What I am against is the expansion of EU law into areas of law and life that can be perfectly adequately addressed by individual states themselves.
How this fails is difficult to arrive at through theory. "Fortunately" we have examples from practice: Tibetan, Uyghur, and Hong Kong voters in China, Kurdish voters in Turkey, Kashmir voters in India [1], or Ukrainian voters under the Soviet union, to name a few.
People don't behave as atomic individuals, but as members of groups.
[1] https://www.washingtonpost.com/world/2019/08/08/kashmirs-new...