I agree, but those instances happen for a club maybe every 50 years, or ever 10-15 for all clubs across the continent. Unfortunately the top tier clubs do it less now simply because they don't need to. They buy players. Shit, they buy youth players and pass them off as their own, just because it ticks that box for club trained status.
I think clubs like Man Utd or Barcelona will definitely keep producing players but these will be in batches of 2 or 3, it's harder to break into elite sides now. Well, Man Utd are shit but they still struggle to mass produce genuine talent like before, because they can go and spend millions to attempt fixing problems. I agree that we should do far more because there's no reason why we shouldn't be producing our own Rashford or Greenwood, but like you say it is an even more difficult task in Serie A, and as the elite club with massive salary budget and squad the chances of it happening at Juve gets less all the time. We just go and buy a Kulusevski and we're done with it.