Sure the guys making the most money in MLS could hang with a championship team. But you're forgetting that guys like Valeri and Morales are the stars of their team. You fill out two thirds of a team with your typical MLS squad journeymen and the average talent on the team is way below the second tier in England.
Right now the league has stated their priority is sustainable growth - aka - putting out a mediocre product that won't upset the small markets. Until this this mentality is done away with (rightly or wrongly so) we shouldn't be comparing or expecting the league to perform like ones with a $450-500k average salary.