Alright, let's actually talk about this instead of just shitting on Applehorse. Firstly, I find the idea of devoting your life to some big, specific, easily-observable goal and then doing nothing once you've achieved it to be retarded. Maybe that sort of thing is fine if you're a character on a children's television show that's gonna be over in less than a year, but that's not how real people work. Real people rarely tie themselves to stuff like that because real people tend to be three-dimensional and have personalities that let them make life decisions beyond just single-mindedly pursuing a single goal. I'm not going to criticize the writers for letting some of the M6 have more freedom than Rainbow Dash and Rarity, who are the only two who explicitly wanted to accomplish something specific.
Twilight, for example, never wanted to be a princess, let alone the ruler of Equestria. The only real thing she wanted was to learn more about Friendship. Of course, ever since the show jumped the shark with Twilicorn, the writers have been desperately trying to give Twilight more to do in order to squeeze more character development out of her. Rainbow Dash, on the other hand, did not have the luxury of being the main character of the show and having the entire show written around her. After RD became a full-on Wonderbolt, the writers started phoning in RD episodes, either making them "Rainbow Dash acts like a dumb cunt" episodes (28 Pranks Later, Secrets and Pies, Non-Compete Clause, etc) or episodes where RD helps other characters grow (Common Ground, The Washouts, Top Bolt, etc). The only significant exception I can think of is Parental Glidance, which also had a shitty premise ("Hey, did you know RD has had family problems her whole life? Well, not anymore she doesn't!").
Fluttershy has similarly been handled poorly in this regard. Fluttershy's "thing", the animal sanctuary, is introduced and resolved in one episode with no build-up and no pay-off. Despite apparently wanting to build an animal sanctuary her whole life, she has never expressed any specific dreams or aspirations throughout the show. The closest thing to a long-term goal Fluttershy has ever had is to be less shy. We've been having "Fluttershy tries to be less shy" episodes since S1, so eventually, the writers just gave up on that as well. In Fame and Misfortune, the writers basically admitted that they had hit a wall with Fluttershy's shyness, hence why we haven't had any more of those episodes since.
Because Applejack has never really had a "thing" like some of the others, she never really hit a wall like they did. You could argue that the writers' boredom with her has been a slow and steady decay, but that's much less jarring than trying to force something on her. If you really want to try and come up with a consistent theme to Applejack's stories, I would say that her episodes have been focused on gradually preparing her to take over as head of her family. "Family" has been the most common theme in all Applejack episodes, especially when you compare her to the rest of the M6. It may not be much, but it's a very realistic direction to take her character development, and it's certainly more than anything Pinkie Pie has. This episode pulled the same shit with Pinkie as Fluttershy Leans In did with Fluttershy: bringing up the question of the character's aspirations and then resolving them in one episode.
