Its normal that hardly anyone makes it at a major club.
I'm trying to put my hat on from the perspective of back then, and generally they were not perceived as hot generations.
1st lineup
A lot depends on who you are asking about the perception, Barca fans or football fans in general? Maybe it is true for the later but surely not true for the former.
Ondoa, Tarin, Adama & Munir were all very highly rated, with fans talking about Sandro who was missing, Halilovic who is arriving, Deulofeu who is just a year older than this generation. Ondoa was one of the main reasons Onana left for example, Cameroon legend that one.
Kaptoum & Godswill gained hype after the tournament.
Inaki has been hyped way long before the winning team, same with Miranda, Morey, Abel (the U17 team that won Euros and played WC final) I would say Collado and Puig got hype after winning it, especially Puig. Alena who was one year older was the "chosen one" before it.
This generation
More expectation as it is a stronger generation though no world class talent (because the three Bernal, Cubarsi and Lamine have already arrived). Guille and Toni are the next level behind but already in B.
Diarra is the biggest talent but slightly skewed as he is a 3m signing who didn't play top level for months, should have been in the B and is adapting.
Defense no super highly rated (well Cuenca was and I think Kospo now is overtaking him), but any of the 4 could make it ala Casado imo.
Midfield, Kim is in that Riqui Puig territory of a very very good player who may end up undersized to influence his game at the top level. Or atleast at the elite level for Barca. And there is a ton of talent backlog to compete with.
Attack. Alba and Pradas not expected to make it. Juan going under the radar and probably in my estimation ends a LaLiga player at a side like Villarreal if we don't bite the bullet with him. Has solid potential though, but again, so much higher rated competition. Though Juan looked the one a few years back with Bayern looking to poach.
This is how we should look at it.
There is a bit of hype generated now, but with it you need to hit the breaks, it is the usual cycle: we produce some talents from La Masia, people then look at every youngster in it under the microscope, get hyped about it as they dominate other youth teams, then set ourselves for disappointment.
You can already see some fans complaining about Flick use of the academy, and how he should do better. It is still
unpopular opinion but by next year I expect it to grow if he doesn't hand few more youngsters a first team squad. I've seen it with Xavi last year too.
There is now folks who expect us to be set with fullbacks because we have Landry and Torrents . I mean, that is too much to ask from the coach, isn't it?
You also make good points about how the tide changes with those prospects. Virgili wasn't highly rated before he season, now you have a guy like me hopes we can see him with first team
Cuenca was more highly rated CB, now it is Eman, and as you said, there is always the Mingueza/Casado examples, guys who made it against the odds.
The 2006/2008 team has already paid what it's due with Lamine/Cubarsi and Bernal, anything more will be just extra bonus. Most of those who got those wins are going to enjoy a successful career elsewhere, and it will still be great success for the academy.