I have a lot of opinions on the story, but the thing I'll focus on for now is Meteion and how her introduction causes so many problems with the plot that it's obvious she was shoehorned into it because the writers didn't want to follow through with what they started in SHB and make Hydaelyn a villain or at least a morally grey character.

I am convinced the writers never even planned on Meteion at any point until they were halfway through writing the plot of Endwalker.
She introduces a lot of plot holes, such as why Venat didn't bother using creation magic to create something to fight her instead of committing mass genocide. Hermes was also already aware of Dynamis before the Meteion incident, so wouldn't it have been better to leave him alone to find some way to counter the dynamis since his memory was wiped and he would have no reason to let the attack happen?

Also, the time-travel stuff doesn't really work well with SHB's time-travel. Graha's original timeline doesn't really work with the idea of there being a stable time-loop if the WoL is dead before they can time-travel, which would mean the Venat in that timeline would never have met the WoL and never found out about Dynamis.

And what was up with the plan to evacuate the people of the planet with the moon to some other planet? Didn't they say that planet was unusually rich in aether? So, wouldn't leaving just make things even worse and leave everyone defenseless?

The more I analyze the plot, the more flaws I find!

It seems to me like they ended up introducing Meteion in an attempt to contort the plot into justifying Venat's actions, but it just makes things worse the more you look at it.