Earlier quoted context omitted.
Huge numbers of young people learn traditional music notation all the time, yes, but I wouldn't say with little stress. Music notation evolved much like English, and much like English it's widely recognized to be full of kludges and unnatural constructions. And similarly, changing it would resemble switching to Esperanto.
To add to your point, many people already use other systems. Tablatures are very, very common for guitar. Lead sheets are used in jazz, and they do away with many of the problems of regular notation (notably, the legibility of chords, and different clefs) by only using it for melodies. In a way, traditional music notation is really only used in classical music. And they're never ever going to adopt another system. Th…
And jazz and pop and rock and.... It is a universal language that allows musicians from many backgrounds to come together and play a tune together. Jazz is the most obvious example--where musicians often sightread a tune together. (Although, to be fair, a substantial part of jazz notation is chord symbols, which are not (directly) a part of traditional notation.)