If you are good enough age shouldn't matter. If you have the talent to make it to the first team you should get playing time and train with the first squad. Now I know Italy has a different mentality when it comes to youngsters but now that Italian clubs can't buy anyone they want with the FFP they should care more about developing young players who are already are familiar with the club and the system etc instead of having 4 or 5 back up players for one position because they are afraid to play youngsters and imagine the 4 central backs are injured...
And offcourse young players will make mistakes and be inconsistent but so are the ''experienced'' players as we can see the last years at Inter. In the long run you will have much more to the young players and players like Vecino, Joao Mario etc who don't give a f*ck about Inter or the fans but only about their salary.
It works both way: When you develope players into better players and sell them for good money it attracts other players to choose for Inter because they know they will get a chance and not be loaned out untill they are 24/25 and then to be sold. I can imagine young Italians won't choose clubs like Inter, Milan, Juventus etc because they know they will never get any chance in the first team. Now we just selling young players to cover the FFP which isn't a bad thing but it's just plain stupid to sell your own players and buy them back after some years for millions more. Like they are going to do with Gravillon if you believe the rumours.
Mediocre players can easily be subbed for young talented players, what is the point of having a youth Academy if you are not using it correct.