VP is most definitely not a waste of time. I trained with VP for several years and it was very effective (even with the errors I described above). Anyone who does not have a power meter or smart trainer should definitely make the very small investment necessary to get up and running with VP. Power is a great training tool AND understanding power by riding with it also gives huge insights into pacing and how “going fast” and training actually works. If you ride with power, real or virtual, you will be both a more fit cyclist and a better, smarter cyclist and racer.
All that being said, real power meters, whether as part of a smart trainer or on the bike are more accurate and better tools than VP if you have it in the budget to make the necessary purchase.