I always wonder how many of these "talents" could have had different career paths if some things had fallen differently for them. Or if they just had stronger mentalities. Or if they worked harder on their weaknesses, always did their best in training, etc.
You can judge players on talent but there is a lot more to being a top level footballer, or any team sportsperson. We've all seen players who seem to have modest talent in comparison to others, and go on and have strong careers, whilst their better teammates in the youth levels fail.
I used to be up on youth players based on just perceived talent and learned the hard way like most others, but I find it just as interesting following the trajectories of players now, as much from a social perspective as sporting.
There are a few players you see who come along maybe every 5 or so years who you know will have good careers. Lanzafame wasn't one of them, but he had good potential, maybe even better.
This is a selection from around 2004 to 2017 that I have tried to grade from their time with the Primavera;
Tier 1 - Giovinco, Kean
Tier 2 - Spinazzola, Palladino, Criscito, Marchisio, Immobile, Marrone, Rugani, Audero
Tier 3 - Chiumiento, Lanzafame, Pasquato, F. Rossi, Mattiello, Clemenza, Cassata, Kastanos, Muratore
The rest you could say they might make it, but they were probably never destined to get out of Serie B. Giovinco and Kean were the only two I was convinced about, and neither may totally prove it. Some internationals here, some total flops, but from my memory this is how I would grade the players I saw.
From our current crop up to 19 years old I'd probably pick Fagioli between tiers 1 and 2. But with him, as for Ranocchia or Dragusin, it's harder to judge now because if these players were still playing U20 Primavera level, as all of the above did, we'd think they were the next Pirlo, De Rossi and Gica Popescu. The U23 team has been an important step to grow these kids faster.
Usually by U21 international level you can see more of who is a potential player and who isn't, but after that it comes down to some of the things I mentioned at the start.