I'm sure soccer is fun to play, and I have many acquaintances (mainly under 40) who played it as youngsters, and some who continue playing into adulthood.
The discussion is about (1) soccer as a spectator sport, and (2) soccer when compared to other sports that one might play, specifically in the U.S..
Spectator sports can be assessed on their level of excitement. In baseball and football, there is the POSSIBILITY that a game-changing event might occur on every single play. In basketball and hockey there are brief periods when the ball or puck is out of range for scoring, but once the ball comes within range of the goal, that possibility exists. Thus for the "major" sports played in the U.S., there is at least the possibility of a game-changing event occurring almost all the time - even if it's a low-scoring game.
In top-level soccer, for MOST of the game, the ball is so far from the goal that the chances of a goal being scored is close to non-existent. All of the other activity (dribbling and passing the ball) is meaningless in determining who wins the game. It may be fascinating to people who have grown up playing and watching the game, because they can appreciate the level of skill required, but to the casual observer, there is nothing fascinating about anything that happens more than 50 meters from either goal - and unfortunately that is for most of the soccer game.
Aside from in a relatively few hotbeds of the sport in the U.S., our top athletes do NOT play soccer, or they play it along with other sports. If and when they are forced to choose one sport or the other (usually due to time constraints) the other sport always wins out. The players who are totally dedicated to soccer are not the top athletes in the student body; it is occasionally said with some cynicism, "The soccer players are the kids who can't play ball." (Many football and basketball coaches steer clear of soccer players because their running style is developed to be able to change directions instantly (moving east to west), rather than getting to the objective quickly (north to south)).
And this is one of the unspoken reasons why soccer will not be a "major" sport in the U.S. anytime soon: the best athletes are playing other sports. In Europe and R.O.W., the best athletes are usually playing soccer, but here, the best athletes never play soccer beyond high school. They are into other sports.
And dare I say, the potentially most fertile ground for "breeding" good soccer players in this country would be the American Inner-City, but African Americans are conspicuously UNinterested in playing soccer. Until Black kids start playing soccer, we, as a country, ain't goin' nowhere.