LiveView was still before v1.0, hence the churn, but Phoenix itself did not introduce breaking changes since v1.0, released more than a decade ago. Our skeleton for new applications change, as best practices around web apps are still evolving, but it is completely up to you to migrate. As a reference point, most other web frameworks have gone through several major versions in the same time, changing how new apps are built but also breaking old ones.
The idea that Phoenix is also mostly macros does not hold in practice. Last time this came up, I believe less than 5% of Phoenix' public API turned out to be macros. You get this impression because the initial skeleton it generates has the endpoint and the router, which are macro heavy, but once you start writing the actual application logic, your context, your controllers, and templates are all regular functions.