As a parent of 3 kids who have more lego than they know what to do with, I disagree. They've got a ton of lego city stuff, a few technics, and a couple of the character/themed ones. That's enough to cover the living room floor about an inch deep, with a few spare pieces to hide near their beds for me to step on at night.
There are special parts, not that many of them really. A lot of them can be worked around with a little builder's ingenuity. The special parts that are the most annoying are the ones where we have one or two, they're small, and they're somewhere. Not where we're looking, or where we've been looking for the last half hour.
My kids build the kit design once. Then the pieces go into the bins. They'll build it again, in motley color schemes, with adaptations. They'll build boats, cars, towers, trucks, and spaceships. And some things that I can't name, but they can tell you exactly what each piece is for.
And in the last year or so, they've started downloading the instructions for sets that they don't have from the lego site, going through them and figuring out what pieces they don't have and need to work around, and deciding if they can build those items. (This is a 5 and an 8 yr old). At 5, the kid is looking through a set of instructions, identifying pieces, remembering if there is one of them in the thousands of pieces we have, and deciding if it's something that can be worked around. That's pretty good training for engineering.