I dive into this in my blog, "What is your alternative to Agile?" - https://www.ebiester.com/agile/2023/04/22/what-agile-alterna... - but the Structured Systems Analysis and Design Method as well as PRINCE2 were common in the industry, but both were examples of methodologies that took waterfall and codified it. However, the last waterfall project I was on was in 2013. We had formal gates out of each section of the process. (Even there, we tried to make it as incremental as possible, but it was a Fortune 500 company that had an overarching process.)
You also have to remember that there are a lot of software projects that do have a "done" state, after which the project goes into maintenance until there is more funding for improvements. Consider an internal project to turn a department excel sheet into an application. You can quickly reverse engineer the current behavior, go to the stakeholders and get a set of the desired behaviors above and beyond what the spreadsheet does, negotiate a scope, write a small design document, and just go do it. You then demo it at the end and change what is necessary before they start using it. You have a small set of bug fixes and QOL improvements that follow, then the project is handed off to a team managing 500 similar projects overseas and is responsible for security and bug fixes.
This doesn't make sense in product companies for good reason. However, on small projects, waterfall can work.
You also have to remember that there are a lot of software projects that do have a "done" state, after which the project goes into maintenance until there is more funding for improvements. Consider an internal project to turn a department excel sheet into an application. You can quickly reverse engineer the current behavior, go to the stakeholders and get a set of the desired behaviors above and beyond what the spreadsheet does, negotiate a scope, write a small design document, and just go do it. You then demo it at the end and change what is necessary before they start using it. You have a small set of bug fixes and QOL improvements that follow, then the project is handed off to a team managing 500 similar projects overseas and is responsible for security and bug fixes.
This doesn't make sense in product companies for good reason. However, on small projects, waterfall can work.