That's certainly the case at a lot of clubs and with a lot of managers but not Klopp. The first thing Klopp done when he got the Liverpool job was to recall all the youngsters that were out on loan (ones we were able to anyway) so he could look at them and he's repeatedly given youngsters chances in the side too. I think sometimes we don't recognise how big a step up it is from academy/reserve team football to top level PL teams.
@Tombstone mentions players like Suso - he looked outstanding in the youth teams but he's not getting near this Liverpool 11 now and it was the arrival of Coutinho (only 1 year older than him) that showed that and lead to him leaving. Same story for Kent and Wilson, they're into their 20's now but they're a million miles behind players like Salah and Mane. Brewster and particularly Woodburn are huge talents but regardless of opportunities, nobody could say with any degree of certainty that they'll make it to the very top because they likelihood is they won't.