I think those who blame City are sully. But it's clear Sancho made the right decision for his career. As much as I hate to say it, staying for any youth player is against their interest.
We are simply too talented. Young players need game time to be good enough to displace our starters. If I were the Dad of a very talented youth player, Once my kid is 17 we are looking for a club where he can be a starter.
Anything less at that age is detrimental.
If we show that kids will get at least a chance, then many will stay for a time, because City is one of the best places any player , of any age, could be & it's a good 'shop window' also.
Then, of course, they have to start to become playing regulars or they are indeed missing valuable development time. So there has to come a moment when they move on, for their own sake, if they don't make it as a City regular. Diaz is in that position. He needs to play, so he'll probably go.
But we have been losing players well before that moment arises, because they think (rightly or wrongly) that they have more chance of developing elsewhere. And that comes about by them watching what happens at City & evaluating it. If scores of players from previous generations, were completely ignored without even getting 5 mins of Premier League football, when some had turned in exceptional performances in their age group, then why would the next generation of City players assume they will get a chance ? Obviously, they will be looking at their options & several, who we wanted to keep, walked out.
There have been very few players in our academy system, who were so bad, they couldn''t have done 5-10 mins in a Prem season. We allowed ourselves to get a reputation for not bringing through players, compared to the rags, for example, who have a rep for bringing them through, purely because they bung a few in, here & there, to fill holes. Most never do anything else, but it's good PR, for the club & also helps them sell on average players, for decent money.
Unfortunately for them, they now have Jose Mourinho.