From experience there's a motivation, almost a compulsion, to follow the instructions to build the cool thing. Then... they sit there, those bricks never taken apart.

That compulsion doesn't seem present in freeform building, and there's been zero interest in it in our household. I know that's not true for all, but it seems like a lost art. Maybe it's because the IP sets show how but not the why it's constructed in a certain way, so given a bag of Lego most wouldn't know the process of creating something they can see in their minds eye within the constraints of the available bricks.

Not really. Even LEGO Classic has way too many different colors (and only a few bricks of each), and too many weird shapes. Even if you buy a lot of it, it's hard to make your own designs that actually look nice (as in, not having that one incorrectly-colored brick in that one place, and so on).

I for the love of God can't comprehend why LEGO Classic has 4 shades of blue. It makes everything worse.

They still do that. I can go to the store right this very moment and get a bin of bricks. There's no problem here: people who want designed sets can get those, and people who want just bricks to use as building material can get those.