I don't know that Blake is tactically stupid. He is a somewhat limited player who optimized his strengths. Everyone used to look at his speed and say that he should add more defensive elements to his game, but maybe it's just not in him to be able to do so.
blake is certainly one-dimensional
fortunately he played in an era of fast courts, which suited his game, and had the tenacity to recover from personal issues to rise up the rankings. never went further than a quarter final though
despite his lack of a plan B in his game, he's a very likeable person.
unlike say...fish or roddick