The Delta Episode is fucking trash. Go here to this place you've been already, go there, fly here, fly there, talk to this person, battle these weak trainers, repeatedly. Your reward for this is Rayquaza and Deoxys I guess? Thanks, I think I would have preferred exploring a version of the Sky Pillar that wasn't completely gutted on my own.
This is ignoring that Zinnia is terrible.
I remember getting shat on by people for saying that bc of the hype of ORAS back in 2014-2015.
Delta Episode was and is still a pitiful excuse of post-game content.