Thanks for posting the video! What I see here is a classic first movement problem. Steve’s points are solid, so I’ll just add on a little. Basically, it’s all in how you start. I took screenshots from both your video and the one you posted of Lopez.
The camera angles are different, of course, but I think you can see the difference.
Your first movement is into the traditional “balance position” leg lift that’s been taught for ages. This is indicated by the orange line. The problem is this traditional approach essentially stops the motion at the top of the leg lift and then restart it to head to the plate. A pitcher only has 1 to 1.4 seconds (on average) to get from first movement to release!
Notice on the Lopez screenshot that his first movement is to the plate. Rather than being straight up and down, his orange line is angled toward the target, and illustrates what many call a “power angle.” Lopez, like most pros, doesn’t stop at the top or start and restart.
The wall drill Steve provided is perfect for learning the power angle, and best of all you can do it anywhere and don’t need a coach. It’s immediate feedback. I’d suggest crossing your arms over your chest (like an X, so left hand on right shoulder, etc) on the first few, just to get the feel of it. Then go at it as shown in the link. Good too if you can use a net instead of a wall at first. Your knuckles may thank you!