Jefit isn't about video tutorials, but keeping track of your progress in specific exercises, and performing correct amount of volume to progress but not over-train, a thing that becomes harder when you advance and your progress starts to slow down. At that point avoiding stagnation requires a lot more optimization and an app that can tell incremental progress in bench is more motivating than looking at the mirror and seeing very small changes. Also, for powerlifters the mirror is a poor tool since it's not about hypertrophy and body shape.