If my original post characterized United as a pure Footballing Academy a la Ajax, that wasn’t its intention. And I suppose Real is a decent comparison at this point, as they have had at least some first team contributions from Academy players in recent years. But as far as the bigger English clubs go — even following 1997 — United have had pretty decent contributions from its youth system.
Players who started their careers at United, progressed to the first team, and contributed significantly to the first team, among others (following your 1997 mark): Darren Fletcher, John O’Shea, Jonny Evans, Wes Brown, Tom Cleverley, Danny Welbeck, Paul Pogba*, Marcus Rashford, Jesse Lingard. I’m probably forgetting some.
Is it a murderer’s row of World’s Bests? Of course not. But compared to other top clubs in England, it’s pretty impressive.
All this to say (hopefully better this time): A lot of the Big Clubs do not really make an attempt to augment their first team with Academy Players (in England, Chelsea, Arsenal and Liverpool and City are who I’m thinking of). Tottenham (only recently a true “big club”) is probably the only exception.
Again, this is not to argue that Manchester United is still a legit footballing academy. Carrington ain’t La Masia. But does their academy produce talent? I’d say that it has and does at a better clip than most “big” clubs.
*obviously didn’t contribute meaningfully until after being bought back from Juve. Also didn’t “start” at United but spent plenty of time in the youth academy.