Not entirely - there was stuff in magazines, and information was being passed around on the internet one way or another long before youtube video tutorials...Everyone else has either learned from their mates or attended music related university degrees or expensive tuition courses which probably only really exist in the big cities.
But it is kind of an interesting thing that electronic music has gone so completely anti-specialization. You don't often seem to see (or hear about) "mixing lessons" or "sound design lessons" (ie someone sitting with you and explaining why your bass sounds weak and what you can do about it for £15 an hour), which would be a really obvious thing to have by analogy with guitar lessons, drum lessons etc. You don't often hear about people deliberately teaming up with someone who can handle the technical side but doesn't have such a creative spark, probably because it would involve both sides to admitting to not being a "complete" producer. You get a lot of people who are obsessed with the importance of doing all your own sound design, never using presets, never using premade loops etc.
It kind of feels like the final step in an evolution away from the Sinatra style traditional pop where pretty much every element - music, lyrics, orchestration, singing, instrumental performance, recording, mixing, mastering - was handled by an individual specialist.