Hello from a dev manager in a big enterprise! My personal experience after working in an org where the PMO tried to force waterfall and the devs tried to force "agile" is that the key to success has nothing to do with project management methodology and everything to do with 1) interpersonal relationships, and 2) the technical team having adequate domain knowledge to make good decisions while planning and executing on the project/product. Lack of #2 is why many corporations force waterfall -- because they can't or don't trust the dev teams to make intelligent choices, and/or because the business stakeholders can't be bothered to engage with them on a daily basis. It's pure laziness and lack of respect for the software that drives processes.