Flew in for a connecting flight last week on morning of 12 May.
It was chaotic. I had four hours for my connecting flight, so wasn't worried there, but the line took over 90 minutes to get through. Machines for the EES were not working, or only infrequently, and even if you did use them you still had to wait in line to see one of the German border police agents at the window.
Frankfurt Airport is chronically understaffed for this, made even worse by EES requirement.
On my return flight yesterday, had 90 minutes to make my connecting flight back to the U.S.
This time the Passport Control line did move much faster, but still took about 40 minutes to get through.
Badly understaffed by the German authorities, about half the windows were even actively processing anyone,
and in the midst of a lot of travelers still in line one guy left his booth and no one replaced him.
It was clear that the speed really was determined by the Border Patrol agent that you met. Some were getting people through very quickly, but others clearly were not fully trained, didn't know all that they had t do, and more than one to call a supervisor.
I made it to boarding with minutes to spare, as did others in line on my flight back to the U.S. who also were connecting from other destinations.
Frankfurt is a difficult airport under ideal conditions, and these are not those right now.
It's also an airport where my flight from LJU, Slovenia yesterday morning literally dropped us off at the one end of Terminal 1, you then had to get on a bus from the tarmac for a nearly 10 minute ride to the terminal, and then after that bus trip to get to my connecting flight at Gate C, I had a three quarter of a mile walk (and that walk brought you to Passport Control, after which you pass through security).
Lot of people were connecting to the US in the line that you had to wait in for Passport Control, and lot of tension as people were trying to push ahead because of anxiety of missing their flight.
Lufthansa and many Star Alliance flights use Frankfurt, so it is hard to avoid depending on where in Europe you are going or returning from. But damn, if you can avoid that airport you should.