I bet every serious design change aims to alleviate some of the pains that the previous design was producing. I bet it's always an honest "let's make it right this time" attempt.
But every new design also contains certain compromises, and also is found to has pain points that have not been anticipated.
On the level of the designers I agree -- each designer is without doubt doing what he thinks is best, but on the larger scale that prompts redesign in the first place, I'm skeptical.
For example, would it be acceptable/comfortable for the designer to conclude "Everything is fine as is, we've done a pretty good job last time around, let's ship it like it is." ? If not that reflects a systemic bias to introduce changes in the name of changing.
But every new design also contains certain compromises, and also is found to has pain points that have not been anticipated.
So the cycle continues.