Rationing in Europe is hard because thanks to free travel it has to be done in all of Europe all at once otherwise people are just gonna go and shop where it's more available, causing problems for neighboring countries, and doing anything at a EU level is incredibly slow and full of bureaucratic rigmarole.
The EU is by its construction a trade harmonization organization, it's not built for acting quickly and dealing with crises.
I've also heard it used as an argument in a podcast with "armchair generals" (I believe it included an actual general, nvm) about the possible planning/intent behind the whole situation. That is, assuming it wasn't all just incompetence and/or secret self-enrichment backdoor deals between key players operating from the shadow. From what I remember (vaguely), it was argued that serious internal problems within the EU could be part of an agenda. I can't recall how that then would be exploited, beyond just causing chaos in Europe for the sake of it. Still, I could imagine that to be a goal in itself for some of the involved.
The EU is by its construction a trade harmonization organization, it's not built for acting quickly and dealing with crises.