Why is Aatrox considered bad?

He doesn't do any particular job better or more uniquely than anyone else.

Many players don't understand his mechanics. As of now he's a very strong wave clearer and lane pusher. That's his first job. His second is to set up kills for his carries. That isn't to say he shouldn't get kills, but he most likely won't be your carry. The biggest problem is that most people build him as a glass-cannon instead of a warrior/tank.

i believe its due to his low base stats and just meh scalings on abilities, i mean he has a great kit a pretty good one imo just his numbers are kinda weak.

And do you guys think the juggernaut items would be good on him?

Nocturne is a lot stronger then aatrox in my opinion