What was our mantra? "Design a little, code a little, test a little".
Agile re-invented or popularized various ideas that had been around for a long time. As always, you adjust for the problem at hand. Royce, the so-called inventor of waterfall (he presented it as an obviously flawed concept, a straw man), argued for copious documentation. Documentation makes a lot of sense when trying to built a jet-liner, and is often a time and money sink if you are trying to write, say, research code for computer vision.
So, "revolutionary"? I dunno? Certainly many places had taken the deliberately flawed Royce model as the way to do things, and so there was a big change as far as that goes. But I can't recall a time where some form of iterative/evolutionary development method was not known about and practiced, or where decision making was favored over process.
To make this clearer - the Royce-ers patted themselves on the back, and then got hopelessly entangled with process. Yourdon came along. Wow, was that a great process - which everyone got entangled with. Then there was Booch..... And now, we have Agile. The details vary, to be sure, but the fundamentals remain the same. Some good ideas for approaching engineering a solution gets turned into conferences, endless books and training, independent consultants, certifications, requirements to be certified to win contracts, and on and on.
I'm old.
That's not waterfall as used in the conventional sense. A key element of waterfall was/is: "Thus the waterfall model maintains that one should move to a phase only when its preceding phase is reviewed and verified."[1]
>The details vary, to be sure, but the fundamentals remain the same.
I disagree. Agile is distincly different at a fundamental level from waterfall. If you walk into a modern shop doing mostly agile with continuous delivery, you'll find that there is almost no process at all that maps directly to waterfall. Literally, not a single one: not design, not coding, not testing, not building, not deploying. They're all fundamentally very different. Coding is probably the one that comes closest and if the site uses TDD or pair programming, it will be clear how drastically different even that is. [1] https://en.wikipedia.org/wiki/Waterfall_model
That wikipedia article is a bit of a mess, but read the article at footnote 7:
http://www.idinews.com/waterfall.html
I was there. I was on those projects. They existed, and unless everything went perfectly according to plan, they were messes.