The club wasn't shortsighted, they had a plan. Players can accelerate that plan, but Fergie did all he could with Pogba at that time and has always hated Mino for how it ended.
Not sure what has been shortsighted with Gomes either. He was given a contract that is fair and full of incentives. He hasn't accepted it. It's a two way street when trying to negotiate. And Gomes didn't see it all his way or enough of his way. The Mata, Lingard, and Pereria situation was crap for 3 months and wasn't good enough. If Gomes couldn't show his commitment for the club at that time by signing the contract, which isn't something new from the past 3 weeks or anything like that, then why should the club invest more time in him?
There's always a plan in place for these players who are training with the first team and their plan is always 2 to 3 years outlook. The same is with Gomes as there's major transitions going on within the first team squad such as the players who have already left like Felliani, Lukaku, Herrera, Rojo, Sanchez, Smalling, etc. Then there will be questions of Jones, Mata, Pereria, Lingard. In steps up some academy players to fill that void and be the 3rd or lowest level of the first team squad behind the bona fide bench players who make up the match day squad and then the first XI players. If United let go Mata, Pereria, Lingard, all go all at once before next year, United will have to spend a lot of money just to have capable senior backups who make that match day squad, which isn't a good use of resources when you're still a few key players away of solidifying your starting XI.