Re: 30 per cent faster
"is your server configured to use HTTP/2?"
should be nearly all of them by now. Although... I _have_ written http servers by hand before, for things like microcontroller config UI pages and for device control via a web interface [it just made more sense that way]. Support for HTTP/2 requests is pretty much mandatory, ya know?
I think what you meant to say was PERSISTENT CONNECTIONS.
But I agree with at least SOME of your javascript comments. What you did NOT mention was "having 15 different places to load script files from". Micro-shaft does THAT with THEIR pages.
And NOT having javascript at ALL - THAT would be best!
So here's what _I_ suggest web devs do, to improve speed:
a) include ONLY those style elements you actually NEED, in a "<style>" section within the '<head>' section of the web page.
b) embed whatever _MINIMAL_ script you might need on the page itself.
c) use '<table>' for formatting things. Yeah, it's old school, but works pretty well
most of the slowness is because of SLOPPY web "programmers" using WAY too much script, or including (a) 3rd party ginormous BLOATWARE style sheet(s). Seen it, in the middle of cleaning that kind of crap up, in fact.
No amount of "30 percent faster" (or fat bandwidth pipes) will _EVAR_ fix _THAT_ !!!