In general, this is not good. Of course there are specific applications where it's useful but in the general space of applications it would be very limiting.

For example, go to http://square.github.io/crossfilter/ and do the filtering on the 5MB data such that you wait for the histograms to be updated from the server. Instead of the tens of milliseconds, it might be seconds or tens of seconds if the server is loaded, i.e. orders of magnitude slower, not to mention unpredictable.

You can think of the network as a data flow constraint. It constrains latency, throughput, privacy and security; the constraints can be unpredictable (network outage; DoS, MiM attack etc.). There can be many good reasons for wanting part of your domain specific logic to fall on the client side.

In particular, dynamic media e.g. interactive data visualization, games and most interactive things that use data or modeling are best partly in the browser.

We're past the point where the rule of thumb was to do business logic on the server and the client only did the presenting of the view and acted as a controller.

And MVC in the browser doesn't need to be complex. It can be tiny as seen in this MVC lib for React: https://github.com/rajeev-k/mvc-router

It's hard to build in an interactive user interface when you have to wait for full page loads to complete between actions. It can be done with thoughtful planning, but sooner or letter that JS you sprinkle in to do view manipulation is going to be unwieldy.

...is the general reasoning. However, personally, I find that unless you're very well organised, you're not saving yourself much, if anything, in the long run.