The Celestial makes you fail if you try to justify yourself but are a hypocrite while doing it:
(Immortal X-Men#6)
An unwillingness to change also seems to be a reason to fail:
https://cdn.discordapp.com/attachmen...62/unknown.png
(AXE: Death to the mutants#2)
Reminder his reason for giving a thumbs up to Thor is "His hammer says he's worthy, so he must be worthy":
https://cdn.discordapp.com/attachmen...66/unknown.png
(AXE: Judgement Day#4)
Also in the same issue he decides to not judge a kid:
https://cdn.discordapp.com/attachmen...24/unknown.png
He's basically saying "I'm not gonna judge a kid, I'm not a monster", at the same time, he will kill the planet, kids included, because other people didn't pass...
So yeah, shit like this shows he's a hypocrite, and a dumbass, and again, Jean herself in AXE: X-Men points out he's a hypocrite lol.
But so is Shawn (At least according to himself in Immortal X-Men#6), and he didn't pass even though he was being consistent to himself and proud of being a piece of shit:
https://cdn.discordapp.com/attachmen...22/unknown.png
Unless the justification here is basically "Doom passes because he judges himself as worthy, while Shawn judges himself as not worthy", but then that'll have problems with other characters, Destiny and Mystique didn't pass, and they definitely shouldn't, and Mystique sometimes likes to talk like her attrocious actions are for some greater good when she's doing it for herself or just to be sadistic, and sometimes, Doom talks like that too, and he gets to pass lol.
It's also worth pointing out there is occasionally an emphasis on trying to do better, to the point that the Celestial in AXE Judgement Day#4 decides humanity isn't worthy because they'll always do better "tomorrow":
https://cdn.discordapp.com/attachmen...18/unknown.png
So with doing better as another reason to pass, Doom really shouldn't have passed now that he's back to villainy.