> Like, if waterfall of a project can be done in 2 weeks, is it agile now?

Sure. The thing is, the waterfall guys would tell you it's impossible to do it in 2 weeks because you need to have written down everything first. "Thousands of pages" was the terms they used.

Agile guys would point you to the Agile manifesto which would lead you to "working code over documentation" and "people over process".

A 2 week period to go from initial spec to product in a user's hands to capture feedback and make changes from there is much closer to agile than to waterfall. In fact it's more or less exactly some older versions of Scrum (which didn't permit deviating from the planned sprint user stories midway through the sprint, instead changes influenced the subsequent sprint).

That doesn't do justice to either waterfall or agile.

It always amazes me how bad the software world is at keeping lessons learned as learned, especially when compared to say engineering. It's as if every 20 years or so we throw away the books and reinvent it all from first principles, hopefully this time with fewer mistakes overall but usually we end up finding both new ones and re-do some old ones.