The supposed complexity of SPA can be addressed by splitting a monolithic React app into multiple SPAs each rendered by its own and smaller script bundle. It helps with SPA loading performance as well. E.g. an app can have Login SPA, Main SPA, Reporting SPA, Audit SPA etc.

Additionally prerender the index/loading page of SPA at build-time to improve loading performance even further. For many (but not all) websites the resulting performance would be the best it can ever get.

Crisp React facilitates both splitting and prerendering.