No. Drupal is only suitable if an organization requires open source. To develop a fully customized site still saves more time than using Drupal. And your maintenance path will be much simpler.
Wait, is it true? Did you encounter a bug? or browser extensions issues? It may not be as efficient as native, but I downloaded some sample files and repeated them until hit Google Docs limits. It is about 450 pages with some images. It is smooth and usable. There's zero delay. (and only 1000MB ram usage with many broswer extensions enabled. I think it's fair...)