The problem with the EU is that there are many levels of abstraction, and the more links in a chain the more susceptible to corruption it is.

This becomes immediately obvious when you vote for a party who fails to fulfill, or even go against their policies. Then for the EU there’s an additional level of abstraction for the commission. At this level, the voter is far removed from their initial vote and are completely powerless.

There are too many levels of indirection. At least in some countries you can vote on a person representing your town/area. This is one level of indirection less and allows people who aren't just chosen party members to win and then they have incentives to help the region.

In "standard" party democracy there is just nothing that can be done. Calling it democracy as in rule of the people is a disgrace.