It honestly makes me a bit sad when people say “Oh, they should’ve played up how Starlight was a piece of shit for laughs.” That… kinda would’ve killed what I liked about Starlight. To me, almost all of her episodes are already about how she’s a mess of a person. Episodes like On The Road to Friendship, or Uncommon Bond. They aren’t funny to me. They paint the picture of a character who’s kind of a catastrophe even though she genuinely wants to be better.
Starlight using magic recklessly stopped being a plot point for the most part since like… A Royal Problem, and even then, Trixie touched the bottle when she told her not to, before that one.
She certainly learned that lesson far better than Discord, I feel, regarding magic… and probably in general. She’s better at not endangering the entire world because she’s so overconfident, and a bad friend. But yeah, she does come across as… kind of a wreck, in general, doesn’t she?
Her explosion at Trixie in A Horse Shoe-in is also not funny. I think it’s a genuinely well written and emotionally harrowing. One of my top 5 favourite scenes in all of season 9 probably. I don’t think Starlight is a funny character, and at her best I think that’s what works best about her. The emotions I associate with her episodes are depression, worry, and melancholy.
That scene was easily one of the best moments she’s had as a character, and I like how it showcased in full how her anger developed from being egocentric in S5 (even if she self-deluded herself), to outright being pissed off that Trixie had inadvertently endangered others, and was being rather blasé in the wake of that.
For similar reasons, I don’t favor fanfics where Starlight’s shtick is “Comedic Sociopathy,” because she isn’t… much of a funny character, and she generally speaking doesn’t engage in wacky idiocy just for the sheer hell of it, especially notable for the lack thereof after S6. She’s far better suited for being sad, and stressed, and what you said, whether it’s as a result of her own personality, or external pressure.
If there’s any character that you could possibly argue that yes, they’d have been better off without being friends with them, it’d be easier to argue it to be Discord, if anything.