Certainly, the chances of a nuclear weapons attack have lessened significantly, but the danger is still very real.
Over 10 thousand nuclear weapons still exist, held by 9 different countries (assuming Israel still has them). That list includes North Korea and Pakistan. I don't have to say anything about North Korea. Pakistan can almost be called an active war zone. Putin appears to be deliberately antagonizing the States, and has just had his primary income source taken away from him. Incidents have come to light that even the nuclear weapons in the United States are not necessarily overseen and maintained correctly. Maybe some of the other 8 countries take better care, but I doubt that all do.
Historians have concluded that we've been damn lucky that we haven't already had a nuclear incident. Some things have changed, definitely lowering the chance of an incident, but not enough to lower it to zero.
It's a common human fallacy: it has never happened, therefore it's not going to happen.
Some experts place the probability of a nuclear incident in the next 10 years at 29%: http://nuclearrisk.org/3likely... That's a lot lower than the 10 year risk during the 60's and 70's, but it's still damn high. Even if they're off by an order of magnitude, a 3% risk of a nuclear incident is still damn scary.