That’s one aspect. But I would say the fact that existing Phoenix apps can migrate to v1.7 and use other features such as verified routes without going through a major migration is an important aspect that should not be downplayed, especially when other frameworks may have gone through more than one major version in those 7.5 years and broke existing code more than once.
I would say a big philosophical change like dropping Views is backward incompatible. You can’t use old tutorials now.