For example take Klopp at Dortmund and the players they have seen successfully graduate in Gotze, Pulisic, these aren't big powerful players. Vast majority of Barcelona's players are not big powerful players though Pique and Busquets stand out as tall players they're exceptions.
The clubs with the most productive styles for younger players tend to be more technical. It's very hard to being players through in a more powerful, physical, dominant side. Even big young players are rarely ready to mix it in say a Mourinho or Benitez side if they're not defenders.
Even players like Matic and Pogba had to move away and then come back. I think each manager from Klopp, Wenger, Guardiola have certain ideas about right now and ideas about the future. Criticisms of wenger is that he's too much long term sustainability but that's seen him be a manager across two decades.
Some would say Mourinho is too focused on the now which brings great success but gets him sacked from big clubs when can't sustain it. The difficult is Arsenal fans now want titles and they understand that the system Arsene created has sustained them through being unable to financially compete.
Now they want change and they want short term success and you can understand that.