MLS has never been a high quality league, primarily because the players are of a lower cognitive competency. Call it a simple observation but, it's factual. Most MLS players couldn't perform well in T2 or T3 Euro leagues because they can't process the game well enough. It's why most of Concaf soccer is so weak, a reliance on the physical at the expense of the mental aspect of the game.
Moving on to Messi, he has been a delight to watch and has elevated a few of his teammates play, Taylor being a prime example. Some of them will parlay their success with Messi into a bigger cheque down the road.
It seems like you are making some stern point to be contrarian (or anti-MLS) on purpose. I've followed international soccer for three decades as a fan and have never heard of this new metric of "cognitive competency." Like any other (relatively) "startup" league, MLS cannot compare its best to clubs with an international brand.
If I had one hundred billion trillion dollars, I could buy the world's most in-form players every year and defeat my rivals my accumulating all of their assets.
You can make a point that the American path to professional soccer is inferior to that of Europe and South America, and you'd have a great case.
I googled "MLS global ranking" and learned that it is anywhere between 10th and 29th. I considered that last ranking to be very dubious; it seemed to be from a made-up firm representing Christiano Ronaldo... but I don't know, and who does?
MLS teams have decreased in quality since they've kept adding expansion franchises every year. The brass in charge wants to have a 32 or 40 team league with no relegation. I would prefer the standard of play and coaching to be better, but here we are.