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.