The first issue that caused the issues, the fire system, was designed to suck air underground, because the architect did not want a fire system to obstruct his roof, never mind that smoke and hot air naturally rise. https://www.thegermanreview.de/p/the-real-story-behind-berli...
Everyone associated with BER is now tainted by association.
If you hire a design team to create a car with a massive hole where the engine and wheels should be, because it is more "clean", and then neglect to hire an engineer to check their work is feasible, is it on the design team or on you being incompetent?
You can say all you want "hot air naturally rises", true, but I doubt an architect has the training to be a safety engineer, and before you say "oh well that's obvious", consider that heavy objects naturally fall to the earth, and yet we have airplanes.
They had a design which would work, but nobody in charge actually did the legwork of bothering to check if it was feasible or not, and/or bungled it so badly even if it were feasible it was like attaching a helicopter to an airplane and then wondering why it didn't fly...
With Lufthansa, I'd assume that FRA is super busy and didn't actually have a gate available at the time; a 747 is a really large aircraft to load using buses.
The last thing I want to do after a long and tiring flight is load up into a bunch of packed buses.
If you choose a normal airline and fly to any reasonably big airport that's not overcrowded, you'll get a jetway outside exceptional situations.
Spoilers: he designed BER for fast passenger transit, just like Tegel, but the airport authorities wanted more shopping space. So they crammed as many shops as they could in detriment of the passenger experience. And then there's the situation with the rise of low-cost airlines who weren't allowed to use the jetway...
I definitely recommend listening to the whole series. It's really well done and a must-listen for anyone with interest in project management.