With the Applewood Derby upcoming, the Cutie Mark Crusaders want to try out something new, and enlist their sisters to help them. Unfortunately, for various reasons, the older ponies take charge of the projects, and ultimately prevent the younger ponies from getting the carts they wanted.
What this show, and especially this season, has often done to liven up such basic plots is to bend them to the characters. "The Gift of the Maud Pie," for instance, might not have perfect characterization, but it takes the old "Gift of the Magi" story and makes it relevant in a meaningful way to ponies we already know about. "The Cart Before the Ponies," meanwhile, more or less just plops three characters we're familiar with into this story and makes them act in a thematically-appropriate way rather than making any effort to compellingly explore them. As the antagonistic forces in this episode, Rarity, Applejack, and Rainbow Dash are painted in a relatively negative light, but it's written so much to theme that any real nuance to their characterizations is little more than flavour.
To be fair, none of the three are necessarily out-of-character, as their reasons at least sound like reasonable motivations for these characters, but for the purposes of this episode they're reduced to their least compelling state. Even the CMC spend more time reacting to their sisters than actually expressing unique traits, and this causes the episode to start losing steam almost as soon as it sets up its main conflict and has little else left to say. There's a serviceable music number, a relatively fast-paced action scene, and a somewhat charming denouement, but as soon as the conflict is set up, the episode doesn't supply anything on top of what nearly any viewer could predict.
Part of the reason for this might be that the episode doesn't spend much time exploring everything it's trying to say. For the most part, it's easy to figure out that the main message is simply not to take the reigns away from someone who's asking for help. However, at the end, there's a few more dimensions given to it. One of which is that kids have a hard time speaking over grown ups, and although this theme is present in much of the episode, it's diminished somewhat because of the sheer exaggerated extent to which the older sisters take over the race. This seems to be for comic effect, but it takes a lot of realism out of the plot and makes it harder to see the real-world messages inside. The episode fails to balance its message of not taking over someone else's project with its idea of how hard it is to speak over adults.
However, it's yet another idea which really gets the short end of the stick. The younger sisters mention expecting the older sisters to know best, which at the end the older sisters deny. This theme, arguably the episode's most interesting, has absolutely zero presence until the very end. It does, at least, explain why the CMC don't make any effort to go against their sisters' plans, but it's not mentioned at least once, and by preventing the CMC from finding their own solution, it makes the episode much more simple and, frankly, dull.
"The Cart Before the Ponies" isn't without its moments, though, especially in the earlier parts. The cold open, where Cheerilee gets a speaking role and her students express disdain for learning, is the funniest part of the whole episode, and seeing the CMC organically interested in doing new things is great even if its potential is entirely wasted. Although RD, Applejack, and Rarity are characterized relatively flatly, their reasons for taking over building the carts is at least initially interesting, and seeing Applejack's resistance to anything nontraditional is funny in its own right. Until it becomes clear the episode isn't going anywhere interesting, these moments - and the slight implications of depth, where they appear - keep the episode afloat.
My Little Pony isn't a show that's ever been consistent in quality, but it's hard not to be disappointed when it reverts to stories this basic. The setting of this derby could have been great for sisterly bonding and friendly cameraderie, and having the CMC explore new things has a lot of potential, so putting all of that to the wayside for an overly simplistic moral-driven story like this feels like a waste. This is the show at its least interesting, failing to offer a whole lot beyond its moral and the show's most basic charms, and after season 6 so frequently managed to be both fresh and entertaining, something this safe and unadventurous is a major letdown.