Twilight's Kingdom was the peak of G4, it was all downhill after that.
For years both bronies and /mlp/ complained that there was a lack of potential in the show and that we needed to see the princesses do something or actually show their power. Yet when it happened the reverse started, complaining that the show is "muh dbz now!"

Tirek was a generic villain and yet he was still one of the most intimidating antagonists the series ever had.
He managed to be a threat to Equestria that actually got shit done and arguably he even won for a time. He wasn't a villain that just dicked around while the mane 6 went on their adventure. The longer the mane 6 took the stronger Tirek was becoming. We got to see him overpower and depower Equestria with little effort.
I also commend them for putting Discord on the bench during it too. If Discord wasn't even in the episode the complaints would have been "why didn't they use discord?"
It also wasn't perfect. I will fully admit that it wasn't perfect, but if it was completely perfect with no flaws whatsoever, it'd be too "safe" and no one would like it.

Twilight's Kingdom was what the MLP Movie should have been and I would have had no issue if Hasbro re-made Twilight's Kingdom as a longer movie.
I'm not stupid either, I'm not saying the show should become nothing but laser battles and fight scenes but if potential was a power, Hasbro tried to hide MLP's potential like some shitty protagonist. Twilight and Starlight shooting a laser beam and blocking it with a shield is not engaging in the slightest.