Uhhhh, McEwen has dropped out Grand Tours a couple times after the sprint stages. It's pretty normal for a sprinter to dropout after the final sprint stage.

Just because a rider isn't good at multiple stage races doesn't make them 'not a champion'. Is the best pro rider the one that can do well over a 1 stage race? or a 20 stage race? why not a 100 stage race?

Some riders care about being able to win a stage, some care about being able to win a climb, some care about TTs, some care about being slightly above average in all of them to win GC.