They're not exceptions that prove the rule. Young players genuinely and generally have very different development trajectories. You could just as well say those teenage stars are the exception that prove the rule. There is no set age at which you can expect a young player to have reached the level he's going to reach.
You do need to play football in your formative years, but you don't necessarily need to do it for United.
Conor Gallagher is the prize example, I suppose. Chelsea and City have developed loads of good players through loans in recent years. They haven't chosen to keep most of them, but that's a different matter. They have represented very major transfer income though, so that is very viable asset development. Just because a player haven't stayed at City or Chelsea doesn't mean he hasn't developed into a very good player.
This is where I have fairly strong opinions on the how young players can develop though.
There are posters who seem to have this idea that footballers will just 'get better' as they get older and that's just a given. I strongly dispute that.
In fact, I would argue that from a technical perspective, the vast majority of footballers will be about as good as they are ever going to be by the time they hit 20/21. Bear in-mind, most of them will have been playing academy football at the various different age groups for the best part of 10 years at 21, so I find it highly unlikely that somehow a player is just suddenly going to get better at shooting or passing or tackling or any of the core technical skills at 21+
Plus, most footballers will be in their physical prime at about 21/22 until about 28/29. There used to be this feeling that footballers had a shelf-life into their early 30s but the demands and the intensity of the modern game are increasingly making it difficult for the
majority of players to continue at a really elite level into their mid-30s
Now, of course, we can and do see many players develop their game post 21+ and become better players, however, I feel this comes with maturity and experience, which have a greater impact on the tactical/mental side of the game and as such, players learn to become 'more effective' but not necessarily 'technically better'.
Take Ronaldo and Rooney as classic examples of how young players can develop and improve.
Ronaldo was a 'show pony' when he arrived at United. Incredibly technically gifted but someone who would seemingly rather beat three defenders than score a goal or provide a match-winning assist. SAF and his coaching team spent countless hours on the training ground with Ronaldo turning him from talented but ineffective into a goal-scoring machine
Likewise, when Rooney arrived at United he was world-class technically but a raw bundle of energy and aggression. He would charge around the pitch like a dog chasing a tennis ball (his nickname at Everton was actually 'dog') and he would be wasting his time and energy playing in the wrong areas. Therefore, his goal-return was not as good as it could have been.
Again, as he developed and he learnt to use his aggression more positively, curtail his temper and improved his tactical understanding of the 'right' areas to play in, he became far more effective.
Now....contrast that with some of our modern-day young recruits/academy products. Rashford is a prime example of someone who, in my opinion, was always going to be capped by a lack of elite technical ability. I don't care that he was only 18/19 when he came into the team, there were too many poor touches, erratic dribbles, bad passes etc...which suggested to me that this was a player who's 'physical' level was good but who's 'technical level' was average at best. Therefore, he was never, ever, ever going to be a Ronaldo, a Messi, a Rooney or an Mbappe who all possessed unbelievable technical ability at 18/19.
That's not to say Rashford can't be useful and/or cannot be coached to be a
more effective player....but it does mean the coaches should have identified this earlier and moulded him accordingly. They have not done this and we have seen his career stall.
In contrast, Shaw and Martial are two examples of young recruits with excellent technical ability. Both of them posses superb footballing attributes, close control, passing ability, comfortable in possession etc...however...neither player has been coached as effectively, or has had the same desire to improve, as players like Ronaldo and Rooney.
So my point in all of this is that the club need to get far, far better at understanding where our young players are at and what they need to develop. If that's a loan to gain experience of playing men's football then great...but they're not suddenly going to improve technically for spending a year at Birmingham or Swansea...so if they don't have those skills at 18/19/20 it's probably time to be thinking about moving them on! If they DO have raw technical ability but need to develop the physical/mental/tactical side of their game and/or just be tested in the faster, hectic environment of men's football...again...great, get them on loan in the Champinship.
If, like a recent Academy graduate who must not be named, they DO have elite technical ability at a young age...then they should be starting games at 17/18 or at least involved on the bench and getting minutes. At that point, it's down to what they have between the ears and the skill of our coaches to get them on the right track and to help them develop their mental/tactical game to add to their raw ability. You will notice, these players
rarely go on loan. Again, someone is going to come out the woodwork and give me the 'exceptions that prove the rule' but I can't think of many elite level players who went on loan at 18/19....other than David Beckham, maybe.
It's not really rocket-science, it's just something we have done very poorly recently. We seem to put academy lads or young players on a pedestal and just assume that they'll hit 23 and suddenly be brilliant just because they got older. This is nonsense and illogical thinking...we're also failing these players by not helping them maximise what they have