Thresh is a "mind-game" champion, so he's good for preying on people who don't know better, or playing with their heads pretending you're going to get them, and so on.
Yes, if the enemy is smart, he becomes less effective, while champions like Taric just brings utility that's useful at any time.
Still, you might just have been lucky meeting bad Thresh players. He's pretty new, so people aren't completely used to him yet.