Susuto

It’s the pace of the game and lack of scoring that I think turn most people off. It’s nowhere near as fast as hockey or basketball.
It also doesn’t have the intricate strategy of football (NFL) or baseball, both of which have a ton more going on than simply the game in front of you.
If a team is down in soccer, the likelihood of a come-back is lower than any of those other sports. The nail-bite factor just isn’t there.
Soccer does have some of the best highlight reels though, but it takes a lot of footage to round one of those up.

Some suggestions that might liven it up (these coming from someone who’s played the game as a primary sport for ~20 years):
1) Lose the off-side rule. It’s a buzzkill by tanking some of the best opportunities for amazing plays. Would also increase scoring.
2) Shrink the field size. This would inevitably boost the overall pace and give #1 more traction because it would be harder to avoid.
3) Allow substitutions as frequently for outdoor as they do for indoor which is almost non-stop, no limit. Keeps fresher bodies on the field which has more potential to keep the action up.
4) Penalty kicks should be removed and transitioned to some sort of direct free kick. The advantage is waaay too great in favor of the kicker for actual penalty kicks, and they perpetuate that which I detest the most about the ~evolution~ of the game (see #5). And no game should *EVER* be decided by a “shoot-out”. Might as well not even have played the 90 min. game in the first place if it comes down to this. Adjustments 1-3 above should all but eliminate any need for something like that.
5) “the dive” - this needs to die. But it’s directly related the level of difficulty of actually scoring, so they resort to these craptastic theatrics to basically get the gimme goal. And if this is the only way you can win, then either the game itself needs a rework or… you suck! I can’t think of any other sport where this level of dishonesty is needed to score. And it happens way more often than you might think.

For those that want to see the potential of soccer, watch an indoor game in a real arena, not some rec gym. All the above are taken care of like I said. And there are walls which not only keep the action constant by keeping things contained, but they actually change the dynamics by allowing for controlled ricochets and passes you receive from yourself (think hockey).