Project management is happily alive. Thinking Agile in some way solves project management is insane.
Plan out your system, estimate the time to build it (you don’t even need good estimates), execute ruthless change control. It’s not hard, just takes discipline. Ruthless change control is the hard part. That doesn’t mean saying no, it means saying “if you change things, it costs you schedule days”.
If you want a clear cut system, iDesign has some good classes. Imo at least.