I had the same experience as the OP... with my first 5S - first phone was about 75% success rate with the touch ID, and was annoying. A replacement phone for it is now 95%+. As in, maybe once in 20 or 30 tries I have to "try again" or simply lift my thumb and replace it and voila, only maybe .5 seconds of delay. Every other time it's instant. Even outdoors in this cold winter in freezing temperatures. I've been impressed to say the least with the replacement phone's touch ID function.
To reply to the OP, I may have agreed with you had I not needed a replacement phone. On the original I had in fact turned touch ID off cause it failed too annoyingly often. Now, with the replacement phone, I love touch ID.
To the OP and those who have chronic problems with their touch ID, i suggest the same as others in this thread: get a replacement. I truly enjoy the feature now, and have it turned on 100% of the time.