First of all, it's much harder to win major events today. When Sigel was piling up his list of titles, the game hadn't gone truly international yet.
Although Filippino players had begun to show up a little earlier,what we know as the Filippino invasion happened chiefly in the mid-90's and the Europeans were not a major force in pool until about 2000.
Shane's relative failure in the WPA events is not a knock on him but, instead, a confirmation of how difficult it is to best the kind of fields one typically runs into in the world championship events.
The fields are so much deeper and there are so many more good players now than then. So many more players are capable of winning an event now than back then.
Along with Appleton, Orcullo, and a few others Shane is one of the superstars of the game today and his skills at rotational pool are comparable to those of American legends like Sigel, Archer, Hall and Lassiter.
Still, as we so often note on this forum, player cannot easily be compared across generations, and are best compared to those against whom the y competed with.
Shane's career will, I believe, one day be on a par with all the greats, with or without surpassing Sigel's title count.