And how many current persons working on Minecraft are also Modders ?
Probably less than you'd think: lots of people recognise they need to leave their work behind at work and not get too emotionally invested in something they love, because at work they'll be exposed to the gut-wrenching business-decision sausage factory.
Beyond small toy mods id be truly shocked if anyone really was able to muster the strength to go right back to working on product after a long day of working on product, especially in game dev. With it being such a passion driven industry already, too.
In a sense, he created expert mode modpacks before they were a thing, where it is common and expected to modify recipes from multiple mods to make a more interconnected recipe chain.