Linode, Amazon, and Google all absolutely use JavaScript. Tom isn't saying that they use JavaScript on the server, he is suggesting that JavaScript is involved with their website
despite using a different language on the server.
Look, saying "client-side JS apps are damn fast" is a vague statement.
What we are talking about here is the architecture of a client-side application in any language. If you can ship application code to a local runtime, then that application code will always be able to respond to user interaction faster than fetching the results of a UI interaction (like a click) from partway across the globe.
The benefits of Client-side JavaScript applications do not come directly from JavaScript. They come from the architecture you can build when treating the Browser as a runtime for applications.
Progressive enhancement (beyond very small apps) is a challenge to maintain, since UI state needs to be shared between a server runtime and client runtime. I don't think there is disagreement that a pure server-rendered app or a pure client-rendered application would be simpler.
And your comments about shitty execution of web pages and apps could apply to any shitty app. They have nothing to do with client-side JavaScript applications. I expect a better argument than "I once saw a webpage that sucked".