The web has always been client-rendered UI. Markup is data. What's changed is the practice of pushing JSON instead to client-render to markup which the client then renders as UI. Whether this is an improvement is highly situational and probably somewhat subjective.
What hasn't changed is that data management is often easier to let someone else think about, and that routing data between different client apps is often most easily and efficiently done with a single centralized intermediary.
What hasn't changed is that data management is often easier to let someone else think about, and that routing data between different client apps is often most easily and efficiently done with a single centralized intermediary.