At a lower level or Rec ball level I agree. To be able to guard high level D1 athletes you do have to be good. Effort alone without the skill set isn't enough at the highest levels.
Give me the best defender in D3 who gives 110% effort and a D1 guy will score at will on him. On certain plays I do see the lack of effort argument, but over all I don't see it as an effort problem. It's not like are players don't want to be better at D, they just lack the skills to be consistent with it. Blame the AAU circuit, it's a lost art in the modern game. Like I said watch the NBA, defensive minded players are very few and far between.