@ElCid  
Mainly, their total lack of genuine interest in goodness. Still, DIscord was like that once too… and he was also a statue once too. SO you never know…

@hironakamura  
ALL OF THIS.
 
Seriously, if Starlight deserves instant forgiveness after tearing apart time and space to try and kill Twilight because she gave a petty sob story, and Discord is still supposed to be one of the Mane Six’s close friends no matter how many times he screws them over and betrays their trust, what makes these three beyond all help?

@hironakamura  

 
Finally! Someone put it into words!

@neo4812  
Sold to who?
 
 
@hironakamura  
It wasn’t shown, but nor was the statue. Like most things with the epilogue, you can decide for yourself. (But it was still a cheap finish.)

People hate the villains fate because the writers don’t get it. They get flack for reforming villains because they write bad reformations. Their sympathy stories get shoehorned in 95% through their villain arc. Like Starlights. They can go off and kill forces of nature like Sombra who’s just a black cloud with a head and no ones gonna feel a thing for that. But now that they finally found out how to make villains sympathetic, they punish them. Its like they forgot Starlight’s lesson in S7. They even already have the means to depower the villains (Grogar’s bell) but never used it. The best ending would be the villains get away, depowered.
 
Then again, I don’t remember their statue in the time skip. For all we know, they were released by Twilight after her coronation.

As far as I’m concerned, Chrysalis should never get another chance.
 
I think she’s burned every last bridge with Twilight to the ground, which is saying something. I can’t imagine the plans she had regarding Starlight when it was all said and done were going to be remotely pleasant either, and I think she it isn’t implausible she gloated over them to her face.
 
(Don’t get be wrong, not an apologist for the other two, but I think Chrysalis is one of the top two vile villains in G4, easily; having 100% unsympathetic characters can be fun)
 
 
@Vaidelot
 

 
Yeah, I’ll bet Twilight really wishes those words meant something to Cozy Glow… but life can be tragic.

@PeppermintSwirl  
I would argue that any form of imprisonment that could contain these three would be inhumane.  
Being in a cage in Tartarus is not much better.
 
Okay arguably Cozy Glow should be easy to contain humanely,  
she doesn’t have inherent magic-eating powers or all the things Chrysalis can do,  
but that would require the cast to perceive her as a normal little girl,  
which none of the heroes or villains seem capable of, perhaps given her actions.
 
More importantly, I wanted to emphasize that these three are not dead,  
because unlike some works of fantasy fiction,  
petrification is easily reversible in Equestria.

And than it turns up Cozy had a perfectly normal childhood with loving parents, she’s just a manipulative, ruthless sociopath by birth. Poor, poor Twilight…

“judging by my calculations whilst likewise petrified”  
This implies that they’re conscious while turned to stone. So uhh, not much of a humane option.

I dont get why people are melting over this. Either Discord with Fluttershy going to reform them or Twilight give new element of Kindness similar job Celestia gave to Fluttershy.

@neo4812  
I assumed that she was just a midget that grew interested in obtaining power for herself

I bet cozy was a slave sold by her parents and that’s why she hates her own kind