For stop signs, restroom signs, etc. I agree.
But here I am talking about the subject of the OP, Web page design.
Yes,
I have finally learned what the icons from Adobe's Acrobat PDF viewer and my favorite Web browsers do, but those are not issues of Web page design.
Looking at Web pages on the Internet and designed by others,
usually I have to make at best just wild guesses at what the icons do, hover and wait for some explanatory English text, usually too small to read, or just use the TIFO method -- try it and find out.
I can say that in all my
usage of Web pages, I have yet to find an icon on a Web page that I both (A) already understand and (B) have seen on more than one Web site. So, to me, on Web sites, that icons are at times and in places useful is cancelled
by the fact that on Web sites the icons are not very standard. Or, for icons, I can't pronounce them, spell them, write them down, type them in, look them up in a dictionary or at Google, etc. The icons are usually little drawings, but usually I can't see the drawing clearly enough to guess what it is trying to represent. There is a icon getting popular that is a rectangle with an arrow through it -- I don't know what it means, and I wouldn't be able to look it up in a dictionary.
In my Web pages, the user interface is supposed to be so simple that any links, e.g., Help, Home, Inputs, Results, need just one very common English word.
Maybe some Web pages really need icons instead of words.
For icons more generally, e.g., for road signs, restroom signs, applications software other than just Web pages, that's a more complicated subject. For some of the icons for some applications software, I believe that some well written technical documentation is missing but needed.