1: Why can't Lacey, Amad too, be considered to ocasionally play from the left ? Why would you consider this detrimental to his development, his quality, his career? This needn't be for 90mins..you know that, right? You know players can interchange, during a game, especially attacking players? Or maybe you think that stopped in 1995?
When did I say it was "detrimental" to their development? I said it was utterly pointless. And it is. Messi, Salah, Mahrez etc. didn't need to switch to the left-wing in order to develop in to the top-tier players in their position. And the clubs who had such top-tier players didn't waste them by putting them where they were less effective. How often did Liverpool or Barca swap Salah and Messi to the opposite flank?...
Even though it may not be detrimental to the players' development, it's still ultimately a waste of their abilities to play them in their less effective position, and detrimental to the club in filling a spot with a square peg.
It wouldn't only be "occasionally" either - if you did try and start Amad and Lacey as the two wingers, then every single minute they were on the pitch together you'd have to play one player out of position stuck on the left flank. Again, going a whole match with a player as a square peg is detrimental to the team.
2: re Foden: you clearly know more than Pep Guardiola. I don't. And that's your opinion, which is fine, all subjective etc...
It's very rare that Pep actually puts Foden wide left. Even the few occasions nowadays when he's on paper the left sided attacker, in reality he comes narrow and acts as a 10. The few times Foden was tried wide left by Southgate for England to try and shoe-horn him in to the side, he didn't really work there.
3: May I also assume, based on your responses, that you think Carrick and his coaching staff, have got it completely wrong, and Dorgu, playing on the left side of midfield and attack, has been an error? Has made our team, actually, worst? It destabilises our team, rather than providing some balance? And that Dorgu would be far better playing from the right, correct?
Dorgu played all of 3 matches there, the first of which was out of necessity with Mbeumo and Amad still at the Afcon.
As I have said a couple of times before though - if your brain is actually capable of ever remembering anything I say - I did state that in order for a player to really be effective playing as a winger on the same side as their favoured foot nowadays, they need excellent pace in order to be able to beat their full-back down the outside. If they don't have this then they hit a dead-end with the ball as they can't burst forwards beyond the defence. Dorgu, as I pointed out, does at least have the pace to get round the outside sometimes. Lacey however, does not have Dorgu's speed to get round the outside of the full-back.
At this early stage in Dorgu's Utd career, I don't know what his favoured position is tbh, whether it's even as a winger or full-back.