It was always a "no true scotsman" issue. If it didn't work, it was because we didn't adhere to it and didn't gather the requirements completely enough. So, sure, waterfall never existed in the sense that it never worked out, but it certainly existed in the sense that it was pursued to the tune of countless man hours and countless dollars.
It was also the only process I learned in college ('94) and was strongly advocated in my classes.
Most attacks from the agile community probably are coming from a place of never having actually seen or practiced the real thing however. For example it does flow backwards at times, it's not the nonsense straight line process that gets straw-manned sometimes.
This is rather my point. In "waterfall" shops I've worked at, the way it has never worked is that the application is completely designed up front, then implemented. The reality is that there has always been iteration involved, and there has always been refining and modification of design, and etc.
The only thing (aside from "ceremonies") I see agile bringing that didn't exist in my experiences with "waterfall" is the notion of bringing the customer in as a constant part of the development process -- which is a welcome addition.
The rest of Agile that I see can be thought of as refinements to waterfall, not as something entirely different.
Yes, it was horrible.
Yes, it got worse when they added the mandatory omnibus all-hands standup scheduled for 8:45-9:00 every morning, that always somehow lasted until at least 9:30, because everyone was continually justifying their existence.
And it was redundant with the spreadsheets that recorded the time spent on any particular task, down to the second.
So much this.
I've been in the industry for about 30 years, and I've never once seen a place that used a methodology that could be called "waterfall" as described by many agile proponents.