I'm probably out of my depth here, but what do you mean by the style sharing cache? I mean, any kind of file can be cached by the browser, including Javascript. And presumably browsers could've implemented optimizations (with or without the aid of hinting annotations) to identify those DSSSL functions that need only be evaluated once.
(BTW, like the author of the article seems to, I actually think that PSL looks like the best of the CSS alternatives he lists).
I severely doubt that. JavaScript can inspect attributes of anything on the entire page, run remote HTTP queries and inspect their attributes, and make styling decisions based on those, on the fly, and in response to user GUI events.
Granted, I'd probably be really okay with these features no longer existing. Just saying, I don't think any DSSSL could have taken them on.
Not sure it would be better (it probably erred on the side of too much mixing of program logic and styling rather than too little), but it would certainly be different.