I don’t think she’s a bad character. Sure, she’s done some questionable things, but so have Discord, Luna, Sunset Shimmer, and many others. She’s learned some valuable lessons after being reformed, but that’s just part of life. Nobody’s perfect, so I don’t think that it would have been right for her to go from pretty much dooming Equestria to being a Celestia style protagonist who never puts a foot wrong.
And she has of course saved Equestria a couple of times.
She’s not my favourite character, and I wouldn’t want her to become another element of harmony but overall, she’s cute and I like her.