Sure, passive content such as nytimes.com can work without JS (although some of their interactive articles would not), but anything more complicated will often be done with client side rendering these days.
Not true, latency scales with CPU capacity on the client. SPAs now exist with client side rendering to mask the bloat in the site plus its dependencies.
If you have a SPA arch but you did a page load per click, you would die. But all sites creep up to 500ms page load times regardless of their starting stack and timings.
Speaking from about a decade of experience with progressive enhancement and all the other things. It is 'much' more. There is an expectation of equivalent functionality/experience in these cases, and you just can't spread your resources that thin to get half a product out that works without Javascript. You're literally development a completely independant application that has to sit on top of another application. Everything comes out 'worse'
These days we invest in ARIAA and proper accessibility integration and if you run without Javascript that is going to get you next to nothing in a 'rich' web application.