The fact that this needed to be said is concerning.
There's no FOUC if you add a stylesheet to <head>, and it concerns me that people seeing that flash have come to expect it as a fault of CSS, when it's really these frameworks making a decision to load the stylesheet via javascript.
I completely agree. I'm promoting a concept called TACE to get back to the principles of the web that were being promoted between 2000-2010. I've realized that a lot of web developers these days don't understand the basic principles of HTML, CSS, and JS because they initially learned web development using a Javascript framework.
I feel like this is an overblown reaction to a single person getting something wrong in the internet? It's not really concerning that not everyone knows everything with a 100% degree of certainty.
There's no FOUC if you add a stylesheet to <head>, and it concerns me that people seeing that flash have come to expect it as a fault of CSS, when it's really these frameworks making a decision to load the stylesheet via javascript.