It was always kind of a cop-out and next best alternative to serious measures to improve your competitiveness. And it risks setting off competitive devaluation cycles.
I'm sure several of those countries are regretting having joined the euro, and not without reason, but leaving it will carry its own costs and in the short run it'll make things worse in each case, not better. And in the long run devaluation doesn't really help the economy at the end of the day. It's only in the middle-long term that there would be a benefit, but either way, it wouldn't save them from having to pass the reforms they have to pass. After all, the euro may force these countries to face their issues more directly than they otherwise would have, but it's not as if the euro causes those issues. Their badly organized labour markets and other economic institutions do.
As you can tell, I'm more in favour of the opposite answer, like many Belgians, I guess. We need more Europe, not less.
It's undeniable that there is a democratic deficit when it comes to those technocrats that you mention. But the local politicians that you also mention should look in the mirror when it comes to finding the ones responsible for that. Their classic game of blaming Europe for all the bad while claiming credit for all the good got old a long time ago. The debacle last month with the carbon emission permit trading scheme is a good illustration of what is wrong with Europe - in itself the ETS was a good plan, and plenty of countries around the globe were following its example. But it was crippled by politicians too obsessed with the short term when it came to determining the amount of permits to be issued, and then killed last month by similarly short-sighted votes in the European Parliament (although I suppose the bright side is that at least the European Parliament had sufficient authority that they were the ones who made the horrible decision, that's progress of a kind).
Whether in the USA or in Europe, subsidiarity is key. The EU is no doubt involved in some things it shouldn't be involved in, but for other things, such as environmental policy or indeed this idea of a European banking union, it simply makes sense to have policy on the EU level rather than national levels. And yes, if we want a single market, a single currency makes sense as well. We need more Europe, but a better Europe, with a European Parliament that actually has teeth, and for which parties are elected based on their European policies, rather than based on the whims of the national politics. In much the same way that so many Americans vote quite differently in national politics from how they vote in local politics.
