It is obvious, in hindsight, that the single European currency was an epically stupid idea. With disastrous outcomes for countries like Greece and Spain.
The UK did well to keep its own currency.
I would still say that the EU was a good idea BUT it did seem to overreach its original purpose, in some ways, over the past couple of decades. Right wing policies such as free movement of labour were dressed up as progressive, left wing policies, and have served to fan the flames of right wing populism.