yes, he can, he will see the modern equivalent of "This site is best viewed in Internet Explorer". Which in 2019 becomes "Please enable Javascript to view this page"
Honestly, such notices are shockingly unusual - most of the time (at least for the sites I encounter) they don't bother with <noscript>, you just get a broken and/or blank page.
I mostly use the web for reading blogs and articles, so the loss of dynamic sites isn't troublesome, but it's certainly not for most users.
(Edit: Some numerical context I have enabled Javascript for 194 sites over the last five years, whereas I encounter several new sites daily.)
> Hmm, I wonder if it's confirmation bias on my end, or just a difference in what pages we each view.
Yes.
Joking aside, I will add that I've been a NoScript/FlashBlock user for quite some time (more than a decade? I honestly can't remember), and while I run into some things that are frustrating (just had to disable NoScript for a tab to order plane tickets), it is refreshingly uncommon.
Yes, you can browse with default deny to JS and Flash.