Agile works very well for small projects. When you have less than 10 developers it gets rid of a lot of overhead. However those are situations where project management isn't really hard and so they didn't need it. Companies doing projects with hundreds of thousands of developers are hurting because nobody can do project management. Agile seemed to help and so they jumped in. However painful experience with agile has shown there really was a good reason for all those processes agile go rid of! They are back to waterfall because at the end of the day they have real problems and all solutions end up pushing them to do a lot of pre-work planning to have a chance. Not that waterfall is good - it isn't - but everything else is worse as painful experience keeps showing.

Note that while we call what they are doing waterfall, in fact it isn't. All (nearly all?) projects are doing releases. They do go back and change things made in the past, just that the timeline is very long. They do discover things are not working and stop - sometimes they don't realize this in time to stop early, but they do stop.

What the world needs is a process for large numbers of people to develop software without stepping on each other. I do not have an answer to this problem - I'm not even sure if it exists.