It would be an argument if there was a causal connection and if it would be due to Seider's (in)abilities, but it isn't. If you insist that 'isn't playing in the NHL' is an argument, you would need to prove that this is due to the fact that a player is too bad, which is clearly not the case with Seider. Seider didn't get the chance to prove his abilities hence the reasons don't have anything to with the actual content and topic of the argument.
'xy is stupid because he didn't study at an Ivy League college' would be a legit argument only if you could prove the correlation between Ivy League -> smart, no Ivy League -> stupid and if one would be able to exclude the possibility of factors like health and wealth having an impact. Ivy-Leaguers neither are automatically smart, nor are non-Ivy Leaguers automatically stupid, and the huge importance of health and wealth to study there are obviously existent -- hence the argument is invalid.
'xy doesn't play in the NHL, hence he can't be as good as a player in the NHL' would only be a legit argument if:
NHL -> very good, non-NHL -> never as good, and other factors could be excluded. We can all agree that NHL -> very good, but the argument would already crumble at non-NHL -> not as good (idk if you are a Ranger, but remember that boy Panarin?). But even if this was the case, you still would need to exlude other factors, which are clearly the reason why Seider isn't in the NHL, which are: age and a global pandemic.
Again, Fox is a fantastic player, even defensively, all of the named are, and he will probably outscore Seider.
But if you consider defensive abilities and leadership as a quality for Norris-contestants, I will say that Seider's chances are just as high as his.
