Remember when I was talking about the moral mandate, this is the downside to it I was talking about.
No, it wasn't. You were talking about something you arbitrarily found less sophisticated than serialized plotting. That's your opinion, I don't agree, that's fine.
This episode was just poorly-written by any standard. I mean, the show's creator came out and said as much. Nobody realized it was bad until the episode aired and reactions weren't what they expected. This happens all the time in the TV industry.
Writing format has nothing to do with it. If anything, it would be more damaging to a show that was serialized to let an episode this poor air, because then the later episodes would have to acknowledge it.
Like... I know you're a big fan of Mystery Inc, but I find the Velma/Shaggy/Scooby plot completely unbearable. I like the rest of the show, but I can't really enjoy episodes of it. Pretty much
every episode has at least one tedious sequence about the stupid Velma plot.
Pinkie Pie's contortions are probably never going to be mentioned again. So I can just lump the episode together with other bad episodes of otherwise-great shows, like "That's Lobstertainment," and never think about it again.
I just can't feel the same way. I don't think it necessarily "sucks" to give a writer a challenge that they have to rise to. Challenges do not just limit; being forced to do things they wouldn't normally do can help to break creators out of their own self-imposed limitations and bad habits.
Basically every book on writing technique I've ever read says you improve the most by working on short stories and essays before you work on longer-format pieces, because short format writing forces you to tighten your pacing and learn how to self-edit. The TV equivalent of short story writing is the done-in-one and most books about TV screenwriting recommend it as a format you need to master. If you can write a good done-in-one, you can write anything. So I really don't think you can fault the show's format here, it's too well-respected.