You're wrong. Look at the responses you're getting, many of us were there in the 90's and if you think waterfall wasn't the dominant method of developing then you just don't know what was going on back then. It doesn't matter if they called it "waterfall" or not, it matters that it's simply what they were doing. Massive requirements gathering and spec writing with development being considered like construction of a blueprint at the end of a months/years long cycle. That's how development was done before agile came around.

Waterfall still isn't dead and will never die because it's how people think by default, plan it all out, then build it. That's how buildings are made and thus it becomes the default methodology of all new managers who don't know what they're doing.