I would say react being the default expands to apps that normally would work perfectly server-side rendered. The insane amount of added boiler plate associated with writing an API, tests for the API (including contract tests), API documentation, API versioning concerns, deployment timing considerations; front-end API integration, front-end state management, front-end tests, API mocks, I feel like there's about 10 more items I could rattle off.
I feel like people forget that web apps can be rendered server-side, and with HTML-over-the-wire (HMTX, Rails Hotwire, Phoenix LiveView, Larvel LiveWire, etc), server-side rendered apps can have a UX similar to a react app, but with far less total effort.