Football is not just about ability. There is a mental side to it that is massive at the top level. You only get that mentality by experiencing real things.
Phil Foden would learn more being kicked and learning to ride tackles and being frustrated at the standard of football, possibly the anger at being left out or brought off and the thrill of a big win infront of thousands of fans, instead of getting 4 assists in a game against Colchester United U23s against players who will be playing non-league in a few years.
The fact that you say you would expect him to fail at Rotherham but if he goes to Valencia you will give him a chance just sums everything up. WHY would Valencia take him on loan??? That is the deluded thinking that clouds our young players, like he can just waltz into Valencia's squad. Ridiculous.
If Phil Foden was to go to Rotherham and not perform well, that's acceptable in his first loan, but i would expect him to use that experience at a better level that is more suited to his ability and perform well in his second and third loans.
If he doesn't, he isn't good enough for Manchester City.
It didn't harm Dele Ali, anything else is an excuse.
You talk about 'improving' from one loan to the next whilst in another thread you are sarcastically celebrating Jack Byrne going from starring v Ajax one season, to Owen Coyle's bench the next.
(I was using Valencia as a random example of a club who played football, it could be any other Spanish, Portuguese, Dutch, Italian, etc etc club. Ie NOT Blackburn Rovers, in a relegation battle or Rotherham).
Most lower league sides in a battle, would pick 18 year old Ishmael Miller over 18 year old David Silva 100% of the time. What use is a small kid who gets knocked off the ball, who likes to pass & move in triangles, in a side which lumps it 30 yards over his head & runs after it ? Why would they play him ? Of course they won't, & probably with good reason. He would have to be spectacular, individually, just to get on the pitch, not trying short passing game with players who are trained to 'knock it'. Miller: fine, big, fast, run after it. Like Walcott, Ali, Oxlaide, & no doubt Sterling, with his pace, would get games. Maybe Sancho would eventually, he's physically bigger & quite fast, but then Brandon Barker got dropped after scoring a worldy., so it can just be politics.
But then if you are generally & genuinely interested, you would know all this & that what I'm saying is true.
The fact you would write off Silva if a 2nd div manager dropped him but applaud Miller, & then see it as success for he academy if he got a transfer to Burnley for a few quid, at the end of it, is why people who think like like you, need removing from the game in this country, if we are ever to stand a chance of producing players like Silva, which we have failed to do in the past 40 years or so, the nearest being Scholes, who was originally a goalscorer & of course never loaned out anywhere, but brought through into the first team.
It's a terrible weakness that we don't have a stronger reserve team competition, which makes loans inevitable for a percentage of players.
But the fact many highly skilled youngsters then fail when thrown to the wolves should be an admission of failure & generate a willingness to improve the system, but unfortunately there are far too many people like yourself, who will blame the kids for not adapting to prehistoric kick & rush results football, rather than realising it is their job to try & create players, not just make them do it themselves.
In the meantime, people such as yourself can point to all the failed kids & say 'I told you so'.