I'm not sure I would consider the time spent learning technologies that are now outdated as a waste of time. This is likely going to be a repeated pattern for the rest of your career. If you regard your past experience with outdated technologies as a waste of time, then you'll find it harder to learn the next new thing. If you stop learning the next new thing, your career as a developer will end. Instead focus on how similar principles can be applied to new technologies as they emerge.