It's not though. EU wide corruption scandals prove this.
Western EU companies routinely pay bribes to dump plastics and toxic waste in Romanian landfills under the disguise of "recyclable material". This way those private companies save a few bucks to stay competitive, and their countries keep getting to call themselves "green" by exporting their environmental damage across the border.
IKEA, plus Austrian and German wood companies routinely paid bribes in the Romanian timber industry to be able to perform mass deforestation.
Austrian companies, like STR*BAG, paid bribes to Romanian politicians to get preferential juicy building contracts, sometimes using EU funds, for highways that never get completed due to various technicalities that got intentionally omitted from the contract so that the building company can just bail out from the deal without having built anything while getting paid in full. Basically, the EU taxpayer is paying for a western EU company to make bank in the east, all through EU funds funneled trough Romania, to build roads that never get built.
All this high level corruption benefits major western EU companies, and corrupt eastern EU politicians a lot. Western EU politicians also benefit from this as the major companies in their countries lobby for them to keep this corrupt system going so they can keep making bank.
The EU is a great thing, but it's also ripe with corruption that's costing the taxpayers tens of billions.
The litmus test is this: can a EU country use european funds to create a new carmaker to compete with central european carmakers? Hell no. But you can spend all european funds buying cars from Germany, that's never wasteful.
The EU has no policy to enrich the entire union, only the central countries. The EU funds are basically a workaround for direct transfers of money from the German government to German companies, via foreign countries.
I'm not from a Eastern European country, but I do live in a poor Eastern European economy, it's the same dynamic.