I have one memory departing from the low cost carrier terminal at Schönefeld. The toilets were broken and the security was saying in broken English to the passengers "this is what you wanted, it's your own fault". I'm not even interested in checking how that miserable place looks right now.

Try to fly from Helsinki, Munich, or even Frankfurt and you notice how bad BER is.

I regularly fly from Munich, indeed more often than from Berlin, and occasionally from Frankfurt. This doesn’t really help me understand what makes it “one of the worst in the EU”.