No, EU is not the root of the problem, whatever the problem is. For example, countries are stronger, more resilient and business is more effective together than everyone trying to do it alone. And of course the EU is not perfect and there is room for improvement.

In my experience, one concrete problem is that so many people misunderstand or are unaware of basic things about the EU and why EU even exists. With the former I mean things like how the EU Parliament is put together, the relation of the EU Commission to the EU Parliament, how is the President of the EU Commission chosen (no, it's not "undemocratic"), what does Schengen mean, what is the Euro and WHY does it exist, why was there legislation which mentioned the curvature of cucumbers, and so on.

As there is no big picture, or it is rejected due to ideological reasons, the lack of knowledge and misunderstandings then manifest as fear of the unknown (=the EU). At this point, these people become against everything in EU: whatever new things are proposed from the EU side, it is somehow "lousy", "bad", "failing", "won't work anyway", and so forth. Any EU company has "bottom-barrel products" and "can't succeed", euro cannot work between countries, Europe is "weak" and "gay" and "collapsing".

Also, some people look at an individual member state and confuse it with the whole EU. For example, the nuclear power stance of Germany is seen as an EU-mandated position and then the whole EU is seen to be against nuclear power. This can also work in reverse: Poland sends generators to Ukraine, well done Poland and why is the weak and failing EU doing nothing (except the generators were from RescEU stores, and one such store was located in Poland, so EU was sending them).

When people understand what the EU is and know the basics, of course they might still disagree with things, that's normal, but at least the arguments are more factual.