so bland and lacking in soul.
How is it lacking in soul? The animation has so much personality:
It feels corporate.
Nothing G5 does is ever as corporate as adding new alicorns to sell toys, then never developing the alicorns.
Underdeveloped characters
The characters get plenty of development. Even the side characters get development.
Sparky
Sparky’s fine. He serves a function to the plot, and he gives Hitch a challenge to overcome.
weird plots
That’s pretty vague.
one of the worst villains in MLP ever
Opaline is a foil to Sunny. She’s a purposeful corruption of what an Alicorn is supposed to be. She thinks she deserves to rule because she belongs to a race of immortal demigods. She’s a dark mirror to MYM’s overarching themes of “Rebuilding” and “Found Family”. She sticks around long enough to get character development, instead of being defeated after two episodes and never coming up again. She has interactions with the heroes, and her power level makes her an appropriate challenge to the heroes.
She’s everything a good MLP villain should be.
Being set in the same universe as FiM for no real reason.
I’d argue that The Unity Crystals give Twilight a better ending than FiM’s series finale did. And given the premise, you might as well set the show in FiM’s future.