Bullocks mate. Youth development is nice and all but its not the be all and end all. Winning trophies and building successful teams consistently (no matter what average squad age) trumps everything else when it comes to the makings of an elite manager. Why haven't you mentioned Wenger? He's achieved more in the game than Klopp and he's great at youth development, wouldn't that make him an 'elite' manager in your eyes then? What has Klopp done in comparison? Hasn't even won a CL (Wenger hasn't either of course).
Also, those Liverpool players you mentioned are far from underachievers. Lallana looked better at Southampton than he has most of his time at Liverpool so far but things are on the up for him this season. Milner has always been a dependable workhouse wherever he's played and Firmino was doing well in the Bundesliga before his move. You make it seem like Klopp is a magician who totally transformed them and thats far from the truth. Dier/Alli/Kane are perfect examples of good handling of youth talent, i'll give you that when it comes to Pochettino.
Klopp hasn't done/won anything at Liverpool yet. Rodgers had a superb season before his final one there and he was doing the same thing with young players