I think that Medvedev is very talented and a good tennis player, but mentally he is still not at the level of Djokovic and Nadal.
The same goes for Kyrgios. Amazing tennis talent but he ruined because of his character and insufficient dedication to tennis.
Since Djokovic is not there, the clear favorite is Nadal again and he now has the opportunity to separate himself from Djokovic and Federer on the eternal list of GS winners and become unattainable to everyone, the greatest tennis player of all time.
As for other young tennis hopefuls, it seems to me that Coric could surprise at this tournament and achieve a good result.
I agree with your point as I am also feeling Medvedev is one of the best player in current generation players, and he can improve in next few years with good experience and no doubt he could be stayed at top for long time like we have three giants in last two decades Kyrgios is also one of the best but due to his behavior we can't go with him for staying at op as he is having some mental issue and need to settle this before having any better results at top level.
Medvedev is surely going to be tough for Nadal which is clearly favorite in this event after Djokovic is not coming due to health issues and Federer is also now out of game for quite long time so good time for him to do his best.
Coric could be a surprise package as he won last event and have good form but still he is unpredictable, hopefully he will improve his game and try to stay here as long as he can.
We also have Alcaraz in the back ground and really improving every tournament and then also Sinner should be also in the discussion in the US Open.
So there are a lot of names specially that this is a Grand Slam and everyone are going to put their best effort to go to the finals and give themselves a chance to win because Djokovic is not entered.
So it's Medvedev, Nadal, Alcaraz, "crowd favorite" Nick, Tsitsi and then Jannik Sinner as early favorites.