The Cup is a hard trophy to win, my team hasn't won it in more than 30 years. I think the fact that the Leafs have only made it out of the first round once in like 20 years is much more of an indictment than the Cup thing.
The Stanley Cup was not hard at all to win during the Original Six era for Toronto and Montreal, considering they had first dibs to sign players within a one hour drive of their respective cities (there was not many hockey players near Chicago, Boston, or NYC during this time). Additionally, each team had a one in six chance to win the cup.
Toronto has not come close to winning a Stanley Cup since the league doubled in size, and Toronto lost their advantage of getting to draft players in the Southern Ontario area first. No cups in 56 years.