Things got really bad in the late 90's and early 2000's before Lego turned it around. My wife got our kids a Lego airplane set with parts that can pretty much only be used to build an airplane fuselage, wings and landing gear. Very sad.
Since then, Lego has drastically cut down on the number of parts they make. There are still specialized parts. Minifigs and car wheels pretty much need to be specialized, and there are a few large parts that obviously exist only to create a larger toy at a cheaper cost. But things are much better than they were 15 years ago. Most sets now consist of mostly generic parts with just a few specialized pieces thrown in.
Kids seem to find ways to be creative no matter what. It gives me hope; the Lego masters of today are the tech geniuses of tomorrow!
Actually using a CAD like program that would give a list of pieces needed and than a way to buy the items online would make my kids a wonderful place. Oh wait they killed that in 2012 (http://ldd.lego.com/en-us/subpages/designbyme)
Also if you go to a Lego store, you can go to the "pick a brick wall" (http://stores.lego.com/en-us/store-experience), and fill up a cup with whatever bricks you want.
Edit: Why the down votes? This link caused me to just surf instead of eating? This was something I didn't realize actually existed. I actually gave him a vote up.
Down votes without explanation is always frustrating
https://farm8.staticflickr.com/7143/6521189607_59acddd58b_o....
[1] http://www.howtospotapsychopath.com/2008/07/31/the-worst-leg...