I don't think I really have a whole lot to say about this, but take a look at the Sens roster the last time they missed the playoffs.
Also, the Leafs roster after their terrible 97-98 season before they made the post season six years in a row.
Is the current Leafs roster worse than either or those teams?
I'd say they are in worse shape the Sens who had a young Alfie and Yashin to build around - though not much more than that (Redden came in the next year). That 97-98 Leafs team was brutal. They added Joseph the next summer.
Biggest change after both of those bad teams - new coaches. Jacques in Ottawa and Pat in Toronto.