As for the punishment the villains got, well there was precedent for it with Discord earlier in the series. The only one I felt maybe could have been redeemed was Cozy, but she's pretty obviously pschopathic. I'm fine with it. They didn't imply they retained any senses while in statue form. It was a way to 'kill' them without actually killing them. Now if they'd turned them into statues and then dropped them off a cliff to shatter, that would have been pretty final ala the Storm King.
As for the punishment the villains got, well there was precedent for it with Discord earlier in the series. The only one I felt maybe could have been redeemed was Cozy, but she's pretty obviously pschopathic. I'm fine with it. They didn't imply they retained any senses while in statue form. It was a way to 'kill' them without actually killing them. Now if they'd turned them into statues and then dropped them off a cliff to shatter, that would have been pretty final ala the Storm King.