But it was established that they could do this in the first episode.
Second episode, actually.
And I have to admit, even though I watched the eps in order, even the first time I saw it the Elements of Harmony and the Taste the Rainbow just felt off. Even the first time, it felt like they were trying really hard to jam square pegs into round holes that they simply weren't meant to be jammed into. That's prolly a large part of the reason I normally say I liked the first half, but disliked the second.
The thing is though, Nightmare Moon's arc was the pilot episode, and pilots are prone to
Early Installment Weirdness. If a concept is introduced in the pilot but then dropped in the rest of the series, it should be assumed that it only happened because the project was still growing roots.
Early Installment Weirdness does NOT mean "this is a perfectly valid concept to bring back later after the viewer has gotten used to something completely different."
I mean, the original Tatsuo Yoshida
Speed Racer manga has a chapter where he fights a lava monster, but nobody says "the manga had a monster, so its totally okay that
The New Adventures of Speed Racer has him fighting cyborgs and aliens!" Likewise, try writing a story where Lisa Simpson is a bratty, reckless, troublemaking kid and telling people "its in character because that's how she was in the original Tracey Ullman shorts, " and see how far it gets you. Bottom line is that IMO, bringing back the Elements of Harmony is just as bad an idea, as if we brought back Bratty Lisa or Speed Racer fighting lava monsters.
Gonna stop here because I keep getting sidetracked writing this post and I need to get done.