1. the browsers were inconsistent in 1990-2000 so we started using JS to make them behave the same
2. meanwhile the only thing we needed were good CSS styles which were not yet present and consistent behaviour
3. over the years the browsers started behaving the same (mainly because Highlander rules - there can be only one, but Firefox is also coping well)
4. but we already got used to having frameworks that would make the pages look the same on all browsers. Also the paradigm was switched to have json data rendered
5. at the current technology we could cope with server generated old-school web pages because they would have low footprint, work faster and require less memory.
Why do I say that? Recently we started working on a migration from a legacy system. Looks like 2000s standard page per HTTP request. Every action like add remove etc. requires a http refresh. However it works much faster than our react system. Because:
1. Nowadays the internet is much faster
2. Phones have a lot of memory which is wasted by js frameworks
3. in the backend all's almost same old story - CRUD CRUD and CRUD (+ pagination, + transactions)