I think 1980s kids who grew up and got well-paying tech jobs are their largest customer demographic now. Kids play Minecraft instead.
That's what my oldest son said, at least; he doesn't see the point in Lego now that Minecraft exists. Breaks my heart. I mean, Minecraft is fantastic, but it's not Lego.
An alternative viewpoint: Minecraft is Lego, and Lego isn't.
When there were fewer themed Lego sets, Lego was a sandbox. You had a mish-mash of generic pieces and your creativity. Modern Lego sets are extremely tailored, both in theme and with sets having bespoke pieces - even if you throw all of your newer sets together in a pile (which people tend not to because each is supposed to be a thing), the pieces aren't as modular, allow for less extension of your imagination.
Minecraft is blocks and what you do with them. Minecraft isn't a digital extension of Lego, it's serving the experience Lego did a few decades ago but no longer does.
There are a lot fewer bespoke parts than you might think. Creating new molds is expensive and if you look closer you'll see that odd shapes are reused for different purposes in different sets.
For some firsthand examples, I have a few of the "botanical" sets, and they have things like Technic wing/fin pieces for leaves, flowers made out of car hoods and trunks, and pink frogs used en masse for cherry blossoms.
They're very creative at reusing pieces. One of the Lego Mario sets has a bomb on a parachute, but the parachute is made out of a white version of the old 3-flower-stem piece.
Overwhelming majority (but not all) of kids I know have parents that limit how much they can play on computer or tablet. They play with legos regularly (among other things).
That's what my oldest son said, at least; he doesn't see the point in Lego now that Minecraft exists. Breaks my heart. I mean, Minecraft is fantastic, but it's not Lego.