BULLCOOKIES! You're talking out your backside.
Lemme clue you in to something, if this was a legit concern there would be articles about it on NNGROUP. It would probably be in the WCAG or it's soon to be launched replacement.
You know why it's not? Because it was taught as a professional writing norm for decades. It's what I had drilled into me TO DO ON PURPOSE when I want "more emphasis".
This "wah wah, they're using caps for emphasis" complaint is typical privileged "graphical screen only screw everyone else" bullshit much akin to that spewed by the framework morons. Again making it painfully clear those who take this viewpoint have never used anything but modern computers.
Why was I taught tis? Because there's no bold or italic when writing cursive. There's no bold or italic on a typewriter. (well, unless you have a dome or wheel changer). The majority of microcomputers didn't have it in their text modes and you didn't work with text in graphcis modes!
SO EXCUSE ME if the first 20+ years of my working with computers and learning to write I learned to use underscore for emphasis and all-caps for "more emphasis".
As to the 100% farce that is the accessibility claim, I can say with 100% certainty braille and the majority of useful screen readers DO NOT GIVE A FLYING PURPLE FISH about case.
The only thing that seems to give a shit is the shit-show that is crApple products, and NOBODY with accessibiltiy needs would or should use their overpriced vendor lock-in steaming train wrecks of rinky, flimsy, half-assed halfwit garbage. At least not by choice.
And such case usage is still required BY LAW in many provinces for highlighting specific phrases, the entities/parties in the document, and so forth. Christmas on a cracker, have you fools never even read a mortgage or rental contract?!?
Well, to be fair probably not. Same reason most of the fools out there writing HTML dont' even realize that <b>, <i>, <em>, and <strong> all have four separate structural and grammatical meansings. And it's kind of a crime that STRONG doesn't default to text-transform:uppercase; since that's is -- or at least was when I was in school -- the writing norm for conveying it!
Good gravy you folks would be so lost on a Trash-80 Model 1, Coco, early Sinclairs, or the plethora of CP/M machines where lower case didn't even exist!