Which sites are you thinking off?

I can't really speak for those sites anyway, or why they are so slow doing things on the client, but like I said, I've written client-side processing and used my 2011 desktop, and there has been no pegging of the CPU or large latencies when filtering/sorting data client-side.

> while absolutely massively complex and large server-rendered HTML loads and renders in an eyeblink.

I've not had that experience - a full page refresh with about 10MB of data does not happen in an eyeblink. It takes about 6 seconds. There's a minimum amount of time for that data to download, regardless of whether it is pre-rendered into `<table>` elements or whether it is sent as JSON. Turning that JSON into a `<table>` on the client takes about 40ms on my 2011 desktop. Sorting it again takes about 5ms.

For this use-case (fairly large amounts of data), doing a full-page refresh each time the user sets a new sort criteria is unarguably a poorer experience than a bit of JS that goes through the table element and re-orders the `<tr>` elements.

In this case, using server-rendered HTML is always going to be 6000ms whenever the user re-sorts the table. Using a client JS function takes 5ms. On a machine purchased in 2011.