Isn't it possible that the idea of sovereignty has been misunderstood within the context of Brexit?
Trading across borders means regulating across borders, and the more you want to trade, the more regulation you need.
‘Sovereignty’ in this context means having influence not only of regulation in your domestic market but in the markets you sell to and buy from.
In the 1960s, Britain experienced the pain of having no control over the European market and too small a domestic market to provide a secure base for its manufacturers.
Ultimately, real sovereignty means having a seat at the table, a voice in the debate and a vote on the outcome.
Arguably Brexit threw all that away: we are left with a paper sovereignty that sounds good but has no effect.