Oh boy, here we go... I'm here because I am bored.
First of all: I am neutral on the Celestial pillars. Both sides have a good argument.
What I am iffy on is Galaxy level and Uni+.
Galaxy level
This is... one tooltip. from one thing. No, a planet level feat does not support a 3-C tiering. Not exactly contradictory because this shit was not hard to do for the pillars, but it does not support 3-C. So... yes this is a one-off statement with little support. Is this more funky than other Terraria tiers like 5-C? I'd say they're comparable, but then again if I had my way we'd downgrade everyone that isn't Endgame rated to Fishron's mist feat as to not have a shaky ass feat be the only thing for scaling.
So, as it stands, 3-C would be fine with how loosely Terraria tiers are treated at the moment, if we put an analytical eye over it, 3-C turns into nothing.
Uni+/Uni
First of all: Uni+ is unsubstantiated garbage because I do NOT see any semblance of time being affected here. cool? cool.
as for Uni... the dryads literally contradict Cthulhu's Uni thing in the same sentence. You don't threaten the fabric of the universe then have the power of the universe used on you so badly you are forced into a retreat and have massive chunks of yourself blown out of you! Seriously, this is not a feat, it's an anti-feat.
Overall: With how loose shit is right now, 3-C is fine, 3-A or Low 2-C is NOT.