Great to see "K. Roll" make it onto WatchMojo's list, even if said list is inundated with random third parties. That channel has 8 million subscribers, more than the number of sales that the vast majority of DK games even make. Not to say every last one of them cares about gaming or Smash, since WatchMojo is a general pop. culture channel, but the exposure is certainly nice.
With both K. Rool and Bowser, neither needs to be the main villain with every single game in their franchise. But when the former has been missing-in-action for the better part of a decade and the fans have wanted him back every step of the way, there's no reason to not bring him back for at least one new game.
Bowser, on the other hand, has become stale as hell. I hadn't read that quote about "Players expect him to kidnap Peach" until now, but not only is that a double-standard with Miyamoto's character always "needing to come back," it's a double-standard in that, if it were any other franchise, he would be cast aside in the blink of an eye because "that's what players expect and that's not fresh enough for today's audiences."