Of course they've had lots of man-time poured into them: they've existed for a long time. But there were first versions of all of those, too, and first versions

Of course they've had lots of man-time poured into them: they've existed for a long time. But there were first versions of all of those, too, and first versions of tonnes of other complex server-rendered sites and apps. Mocking inclusion and front-end performance is quite contradictory to "Use The Right Tool". There are several cases where server-side rendering has a place and there are several frameworks and approaches that help with the complexity, just like there are cases when client-side interactivity is a better choice and you can pick a framework that will help with performance and cross-browser issues - and complexity, which exists on the client side as well.