It has not very good bulk and has only 81 attack, which needs a boost from swords dance. Problem is, it has low bulk so it can't set up. It's unbidden boosts it's speed, but it's already pretty high and only really outspeed a few more things. It doesn't work as a good defogger either. Finally, ubers are a lot more powerful. Look at zacian. Much better. Also, ubers were used in a lot of team for them to get kicked out of ou. Hawluchas isn't see on a lot of teams and thus isn't fit to be an uber.