Time wasted? I disagree. As I stated before, there are a lot of concepts within Wing Chun that are extremely useful in fighting. For example, the centerline concept, sensitivity training (helps a ton with grappling), chain punching (aka straight blast), awesome in-close fighting tactics (Can be used effectively from the clinch). Also, there is one thing that my lineage teaches that others do not, and that is what are called "eye exercises." We train our eyes to move quicker and be stronger through scientifically proven drills. This helps with timing, because you will see a kick developing as it comes and you can move or defend effectively, or apply stop-hits.
All of these concepts integrate wonderfully into my Muay Thai arsenal. Then on top of the traditional Wing Chun fighting tactics, I also have Sport Kung-Fu, which applies slightly different footwork and principles by simply elaborating off of its Wing Chun roots. There are countless examples of effective Sport Kung-Fu techniques and applications because it's designed for the competition scene and the ring.
I don't see this as a waste of time, but I guess it's all a matter of opinion.