Sorry, I think I meant transatlantic airport, or a "large" airport. Not sure, it used to lack something I heard but not sure exactly what and if it's still true. They're struggling with building a new one so something :)
Berlin is certainly underserved given its size but that's just the Frankfurt effect (an airport with >60m passengers p.a. for a city <1m population).
That's assuming you don't miss your connection and lose an hour or two getting rebooked, or dealing with lost luggage.