I think the main issue with waterfall development was the corner cutting at every step. Because software is not as hard to modify as hardware projects, it would

I think the main issue with waterfall development was the corner cutting at every step. Because software is not as hard to modify as hardware projects, it would be faster to do a shitty waterfall plan where the requirements would not be completely understood, and the implementation design lacked some major use cases, and implementation would miss other things like error handling, and the final product would be crap needing fixing. The issue is that it would be cheaper to do it that way, because trying to get all requirements right and implementation right before doing was really expensive and still incorrect in he end. You'd always end with bugs or missing features...