How is shovelware a problem?
If a title doesn't appeal to you don't buy it. You still have other titles to pick from. The problem would be if there were no other titles.
Developers recognize that a bad title catered to the mass market like a movie tie-in will sell, but that quality games sell better. Those bad titles don't cost much to produce. So in order to finance those epic titles, a few duds have to be released.
Consider the movie industry. Romantic comedies typically perform well but are in no means blockbusters (with rare exceptions) however they don't cost much to make in comparison to your CGI stunt action flick which cost a good deal of money and can flop disastrously leaving studios in debt. Yet they are more likely to smash box office records.
The point is the two go hand in hand, and as you pointed out they exist on all three consoles (just in different percentages), historically the more popular console sees the greater amount of shovelware, yet by no means did it doom the console to obscurity. It simply was an avenue for developers to get to the mass market.