A number of non-athletic, not quick players who are more productive rebounders than Yao, none of them 7'6", come to mind.
A 7'6" starter, as "dominant" as he was in the paint, and a potential "all-time great," should have done it better. Maybe it is just my opinion, but it's a reasonable one.
And he wasn't out of shape his whole career? I recall watching him lumber up and down the court every single possession and pick up a ton of sloppy fouls. It has been like six years since he's actually been on an NBA floor, though, so maybe I just can't remember.
I don't know what, "1 out of 5 in Canada we call that a fail, im not sure how your education system would score it." means.