I already knew "The Mysterious Mare-Do-Well" was bad, but I forgot how utterly despicable it is. I'll admit, it looks even nicer than the average episode, but the writing ranges from deeply unpleasant to outright incompetent. It's a shock that this was even given the green light, especially for this show. To many, this is the show's lowest point, and I'm inclined to agree with them.
First off, Rainbow Dash. The episode wants to set her up as going too far with her arrogance, and it achieves this goal and then some. In fact, the episode is so interested in making Dash look bad that it expends a majority of its run time shaming her and embarrassing her in scenes that serve no other purpose. We see Rainbow considering a second hero to be competition. We see said second hero one-upping Rainbow at every turn. We see Rainbow being utterly incompetent. We see Rainbow bothering other ponies in a desperate attempt to feel like a hero.
At best, this is Rainbow at her worst. At worst, this is out-of-character. The sheer quantity of useless scenes involving Rainbow being shamed is thoroughly unpleasant, getting to the point where her friends exhibit the same arrogance (which is even more out-of-character for them) with no repercussions. In fact, the episode continues to just shame Rainbow, and it gets to the point where Rainbow's still the only one who needs to learn a lesson. As such, the actual friendship lesson rings hollow in what is a baffling example of bad writing.
There are opportunities to explore deeper themes. They could have addressed hypocrisy. They could have touched upon Rainbow feeling lonely. But they forsake that in order to continue following their anti-Rainbow Dash agenda. It really does feel like the writer of this episode has something against Rainbow Dash, and thinks the terrible way she's written in this episode is how the character actually is.
The episode isn't particularly well-made, either. The episode doesn't so much smoothly transition from scene to scene as just cut from set-piece to set-piece. There's no real flow to it, and the fact that these scenes serve no real purpose only makes it worse. Combine that with the bad writing, and the episode comes off as far below the expected level of competence for this show.
Despite that, I will admit that the episode looks really nice. The cinematography is some of the show's best up to that point, and the animation is incredibly smooth. There's a number of neat little animations, especially from Rainbow Dash, that are gif-worthy. But that doesn't make up for how horrible the rest of it is.
So, "The Mysterious Mare-Do-Well". An absolutely horrible episode, and by far one of the lowest points of the show. It's even worse than I remember it, and it does almost nothing right. Between a lack of likeable characters, an apparent vendetta against Rainbow Dash, and a lack of flow, this is a dreadful episode. From here, it can only get better. Right?