While I can totally see where you're coming from, I play soldier quite a bit and I like the stink cloud. There are quite a lot of players using it in stupid ways that hinder the team. But there are also so many great situations in which to use it. Rooftop campers, teleporter campers - it's easy to make their position, as I like to say, "less hospitable." Just for one example.
It's important to remember that all things in this game are not centered around their use in multiplayer, but also in coop, where the stink cloud can be invaluable..