I think ECB is doing a terrible job in reaching their stated goal of 2% inflation.
I think actual helicopter money distributed equally to each EU citizen (a few hundred EUR) would have been much better than buying state bonds. Most people would have spent the money immediately and thus caused the desired inflation. As it is now the states benefit from QE in the first step, used in questionable projects in the second step and then it doesn’t tickle down but just inflates various financial asset bubbles. It’s neither fair nor effective.
Of course you need some thought, how to actually distribute the money without losing to much on bureaucracy, but it is possible.