I think there is ancedotal evidence that the biggest System X sets were very slow to construct - I think the space station was notorious? But then equally I just bought a 3666 which came with the instructions that had been ripped up because 'My Dad was so frustrated with putting it together that he ripped them up when he finished building it'. I think it's just the nature of bigger sets.
The big space station has like 300 hundred of those stupid little connectors. If anyone ever thought those are fun.. well....
The difference with Steck is that anyone can probably assemble a building with no instructions. Oh, and it's fun.
("dad" probably wasn't very.. normal. I mean, ripping the instructions when you had a hard time at it makes PERFECT sense, right!? )
Of course it will take time. And of course the more parts it has, the longer it takes. Duh, right?
If people don't wanna spend a couple of hours with their kid anyways... why have one in the first place?!