If the lights and sounds were already there, would you have ever explored the process of adding them yourself?
I still would argue that, yes, I would. Only this time I'd do it using the sensors and special bricks provided. I think it's also worth noting that these add-ons Lego is creating are expensive and will come only with certain kits, mostly created for adult audiences.
I think the kits have probably curtailed creativity in some capacity.
Well, here goes my personal, completely anedoctal experience:
The kits were created during my childhood (so I have some pre-kits ones). With the kits, I would usually open the box, build it according to instructions, play a bit and then completely dismantle it and store with all the other ones. Then I spent most of my days building new stuff with it. No hinder in creativity in there.
Nowadays, I still have all my Legos, and two small godchildren (4 and 6 yo). They love it and eagerly ask to come visit and play with it every weekend. Last Christmas, I bought a new kit to each one of them. And what did they do as soon as we opened it? They completely dismissed the kits, mixed all the bricks and started to build every type of crazy stuff.
This makes me think the experts may be somehow underestimating kids imagination.