It would be madness to sell him, specially for the low prices recorded by journalists.
Who do you replace him with? Yamal? Barcelona will ask for 180-200. Arda Güller? Madrid will ask por 120-150. Wirtz or Musiala? Will cost at least 100.
You simply don’t sell your top talents.
I will start seriously doubting Ineos if they let him go, and replace him with a lesser player.
First of all, 3 of those 4 players you listed are some of the best in the world already in their positions, except for Güler (who won't even cost half of 150m if Madrid decides to sell him) with their career trajectory looking like being the best players of their generation with genuine Ballon d'Or potential.
Garnacho is nowhere near that bracket and clearly doesn't have the potential to arrive there one day, either.
Secondly, here's a list of players that are attainable or likely will become attainable in the next few windows, because this notion that we cannot replace him is just becoming ridiculous now.
Most of these players are superior to Garnacho IMO, especially in the number 10 role. I don't think anyone on the list can be considered objectively inferior to him, either.
Mohammed Kudus
Morgan Gibbs-White
Matheus Cunha
Morgan Rogers
Tyler Dibling
Antoine Semenyo
Nico Williams
Arda Güler
Rodrygo Goes
Xavi Simons
Mathys Tel
Jamie Gittens
Rafa Leao
Kenan Yildiz
Nico Paz
Ademola Lookman
Desire Doue
Rayan Cherki
Bradley Barcola
Pedro Goncalves
You're right that we shouldn't sell our top talents...but those are Yoro, Mainoo, Hojlund, Amad, and potentially a couple of kids that are still playing in the academy. Garnacho is just a good talent.
He had a purple patch when he was bothered, he still had limits, but decided to play to his best attributes. However he has never been in the Suarez, Rooney, Aguero category for me. He could have of he applied himself like Rooney or Ronaldo.
But unfortunately, Gernacho inherited his bad habits, maybe even got too big for his boots, hence both of them getting dropped.
Rashford is 27 with 3 bad seasons under his belt in his career so far, including the current one. Coincidentally, in all of those three seasons United have collectively been performing like a mid-table side, and we're talking about three of the four worst seasons in the last 30 years, with the only comparable one being 13/14 under Moyes...and you're trying to tell me Rashford only has purple patches. 7 good seasons and 3 terrible ones in abysmal teams equals purple patch. Let's not continue this discussion I think.