Surely part of that is because most tech related questions have already been asked and answered on SO. I'd say a decline in new question is stack overflow working as designed. A large part of what makes SO so good is the searchability of old questions. There will always be new questions to ask, as new technologies confuse Devs in new ways, but to expect new questions to be asked at the same rate as peak is to misunderstand what SO is at it's core.

But that's just like, my opinion, dude.