Young Player of the Season should be restricted to U23 and maybe a <50 total appearances requirement as well. This award isn't for Martial who cost >$50M, has almost 150 PL appearances, and 18 senior caps for France or Grealish who debuted in 2013-14 and has been a known quantity for years. I also don't need this award to tell me that TAA + Rashford are really good, that's been apparent for a while for both, they've both been part of their respective first teams for at least a few years each. And if your transfer fee is as high as Pulisic's clearly you're a fantastic player already despite whatever age you are.
The only truly real candidates for this award that received the nomination are Greenwood, Henderson, and Mount. On the basis of just that, give it to Greenwood or Henderson, pick whichever you value more for a young player. I'd probably pick Greenwood. But clearly something is wrong if some of these players are being nominated for "young player" awards. Because of this, you're missing great candidates for the spirit of the award in Bukayo Saka, Max Aarons, Aaron Ramsdale, among others. But that's not as buzzy as having 3 Manchester United players, a future Man U player, 2 Chelsea players and 2 talented Englishmen so I get it.