>Minecraft is one of the biggest games in the world.

Yes, but the set who play enough to get into modding, especially to get into hosting a modded server, is much smaller. I think data from a few years ago was that most sales are from systems that don't even allow modding (it was brought up during a discussion where I was wondering how much of Minecraft's continued popularity was due to modding).

>Playing Minecraft itself has an incredibly wide level of technical scaling, from 'just' building pretty buildings in creative, through to all the pretty advanced redstone circuitry. I'm sure you've seen all the giant functioning CPU builds made from "off the shelf" minecraft blocks?

I've taken part in building them back when red stone first came out, but I think the appeal is still distinctly different than that of editing one's social media site and that this difference can have an influence on which demographics are impacted.

I think minecraft is going to be instrumental to a new generation of tinkerers, scripters, and coders, especially as our every day applications seem to become less open to tinkering and modifying (yes, other options exist on the market, but we are talking children who aren't making the purchasing decisions and what the average family has available), but I don't think it is going to completely fill the gap left by what OP was mentioning.