I can see why that reputation exists, but I think it's to do with expectations. @Duvel
's description is one I can recognise.
Fruh was busy. There was one waiter serving a large room, including 2 big parties. He was a big, muscular, jovial bald man with a loud voice and a large smile. He looked splendid in his apron secured at the waist wirh a beautifully aged leather belt.
Service was slow. The usual raised eyebrow and half-smile wasn't going to bring him scuttling across to our table to see what would make our dining experience more fulfilling and meaningful. Our reluctance to call out "Entschuldigung" because of language shyness didn't help. When Mrs K's order of meatballs was unavailable and she couldn't find another option straight away, he left us again for a while. The beers did keep coming on a fairly regular basis though, and he would chat as he worked. Throughout, he kept the atmosphere jaunty, boistrously engaging with whoever was next.
The room we went to for a nightcap was similarly run by a sturdy young Madchen. She offered us the choices from the drinks menu (in German only) and when I hesitated, recommended "the local beer." Again, the Kolsch arrived regularly.
I enjoyed the no nonsense approach. It's in keeping with the function of these places. The limited, almost identical menu choices suited me fine, and they will suit anyone who likes pork and sauerkraut. I could happily order half the items on these menus, Mrs K could get along with meatballs, and if unavailable as above, Fruh had goulash. 
I found the limited drinks choice in keeping with the function of the room. The Aperol spritzer was advertised on a glossy card with 3 or 4 Aperol drinks. The description of one if these included 3 other ingredients, crossed out with marker pen and replaced with a hand written, "Orange Juice," possibly indicating that only English speakers looked at this card.
So that's what the service was like. No nonsense, friendly without being fake friends, certainly not obsequious. No fake refinement. No one offering a waffer-thin mint to complement the meal. A bit slow. Probably need to speak up!
Anyway, we're here for a few more days, and it won't all be Brauhauser and Kebab shops.