Are elliptical machines worthless for working out or just worthless for my goals?

I was told to stop using the elliptical because I was wasting my time. I have always known that the elliptical is 10x easier than the treadmill, but the trainer who said this to me made it sound as if the elliptical was a bad thing. Does anyone have any information that can either substantiate or disprove this?

Also my 3 main focuses of my workouts are 1) increase cardio/explosiveness 2) build lean muscle while maintaining flexibility & 3) maintain weight (I am preparing for an amateur MMA fight this coming November)