> Bionicle/Hero Factory was by far the best they had for creative play.
I disagree with this premise. Play comes in countless forms, and I think this statement places roleplay above other forms of youthful creativity. For some kids, the roleplay of Lego action figures was a huge draw. Other kids play in different ways.
Some kids (like me) enjoyed Bionicle at first, but got bored of action figures by age ~8. Bionicle's lack of compatibility with most other Lego products meant that I was left with a bunch of parts I never really played with much (except for the ripcord disk-launcher things. I still get a kick out of those!) For me, the next chapter was Technic, because I liked making things that move. Fast forward a bit, and Technic led to Mindstorms, Mindstorms led to FIRST Robotics and Arduino, and now I'm a firmware engineer.
Does Technic have less creative value than Bionicle? I think that's an impossible question to answer. It depends on the kid. Any given object has as much creative power as a child's mind projects into it.
> On the whole it's a disappointing downward trajectory.
Yes and no.
On one hand, today's Lego action figures are pathetic compared to the Bionicle/Hero Factory heyday. It's also easy to mock cheap, commercialized dust collectors like the Brickheadz series. Part of me is sad to see Mindstorms dying off, but I also recognize that, even at its peak (NXT), it was totally inaccessible to most kids.
On the other hand, some things have gotten a lot better than they were 20 years ago. Lego's "Friends" theme is by far the best girl-targeted product line they've ever made. Belleville was the "girl" product line of my youth, and it was was cynical, condescending trash that was so thematically paper-thin that even my 6-year-old little sister saw straight through it.
Almost identical pathway here, except with some Spybotics thrown in around the same time as Bionicle. I sometimes wish Mindstorms had that level of world building...
Emphasis on "creative". Bionicle was was their product line that was simple enough for a child to have a complete mental model of it, and at the same time complex enough that they could build their own "real" adult sets, something that isn't obviously a throwaway pile of bricks.
On the whole it's a disappointing downward trajectory.