A few points here...
1) Royal Bank Plaza and Scotia Plaza were homegrown designs by WZMH, which was the same solid domestic corporate operation then as today; no "world class starchitects" imported to make them possible (and the CN Tower was likewise "homegrown", though John Andrews was more "domestic-starchitectesque" during his Toronto stint)
2) aside from the questionable case of the Torno penthouse, IIRC Philip Johnson didn't do anything in Toronto until the CBC HQ, which wasn't finished until the early 90s
3) by the 60s/70s, cognoscenti were judging Edward Durell Stone as more "world crass" than "world class", and the context-mugging Carrara orgy that was FCP didn't fare any better in critics' eyes--in fact, at least in the eyes of said cognoscenti, to call 60s/70s Stone "one of the greatest architects of all time" would be like calling Jacqueline Susann "one of the greatest authors of all time"
4) remember: when it comes to present day equivalents to Mies, Pei, Johnson, Stone (and the latter two asterisked), we've already had Gehry at the AGO, plus Libeskind (at ROM *and* the L Tower), Alsop, Snohetta, Foster, Behnisch, Maki, Correa, SOM, KPF, etc etc etc.
And as for Marilyn in Mississauga: hey, nothing wrong with that. Good score. And Mississauga's part of the GTA; so it isn't like we ought to be having penis-envy jealousy or anything...