Barcelona lost 3-0 to Ajax who had first teamers playing against them...And in both cases, Juvenil A sides were playing opponents who were 2-3 years older in most cases
There were 3 seasons before Eusebio, B team has existed before - regardless of their classification with Segunda
I don't think I've understood what you've illustrated by showing that Barca youth teams not coached by Eusebio got beaten in the NextGen series in the very first knockout round in two consecutive seasons when you initially wanted to show that all the youth teams except Barca B are doing well.
Eusebio lacking talent was not the argument. You got that wrong so I repeat my point. The argument was about losing almost an entire starting XI and having to reshuffle an entire team from back to front with younger and more inexperienced players from lower divisions.
I don't question the potential of Samper or Traore or Dongou or Bagnack yet at the moment Sergi Samper in midfield is nowhere near Rafinha's or Sergi Roberto's level from last season, Traore isn't at the level of Deulofeu and absolutely no forward is at Luis Alberto's level who got double figure goals and assist last season. Primarily because Traore, Samper, Dongou and Bagnack are 17 and 18 respectively while Sergi Roberto, Rafinha, dos Santos and Luis Alberto are between 20 and 23. Which is a huge gap at that stage of development. Which brings us back to the age issue. You don't expect a squad which has only 2 players older than 22 to dominate the second division let alone enforce the "Barca style" when even the first team can barely do that anymore.
The reference point for Barca B should be RM Castilla. Only compareable team in the entire division.
I've pointed out that every youth team at Barcelona routinely plays against competition older than they are and they flourish...