The major issue with modern football for me (other than me being old and jaded) is how generic and homogenized everything is now. One of the great draws of old European football was how variable the styles of play were, made for intriguing match ups. That variability has been mostly lost, there is little in the overall approach that separates most teams, it is just quality of player and execution.
Not just teams as well, but individual players. The left footed Right Forward who cuts in, recycles the ball, seems like every team have a version of the same player, playing the same way, in the same areas, just with different levels of quality. You can predict what a player is going to do in a certain situation better than ever before, the game has become so hyper analyzed and efficiency focused that the joy of the game has been lost. Stats becoming such an overwhelming part of football discussion shows this, I didn't care about the greats of the pasts stats, it was their mastery of the game, their style and creativity.
I don't know how we get that back, genie might be out of the bottle with detailed analysis dictating what should be done instead of feel.