It's just boring to me, maybe CoD has ruined it. I really liked Gears 1 but didn't play 2 because of the lag, so it's been years since I played MP like this. I think it's dumb that people can be completely behind cover, see you coming and just shotgun around the corner for an instakill. I also don't like the fact that I can empty half a clip into someone and they can just flip away and recover.
honestly i look at gears as more of a strategy game than an actual shooter, some for reasons you explained above. it is a bad strategy to walk blindly around a corner where you KNOW someone may be waiting with a shotgun.
you can have the best accuracy in the game, but if you are getting outsmarted by a team, your accuracy won't matter at all. teamwork and strategies in this game are key.
totally can get why people don't like it for that reason, and reasons you explained above, but to me this game is more of a strategy/smarts game than it is a shooter.
EDIT:
also, the person in cover, if on a corner/edge, they are visible to the other people, IF they are right at the edge. if they aren't right at the edge they aren't visible. but if you aren't at the edge, you can't press L and pop out around the corner and fire quickly.