I'm sure he was a great performer at some lower level to be able to get to the majors, but in that one example, I see a lunging swing and collapsing back leg. He looks like he's about to topple over.
As mentioned above, mechanics only do so much. Seeing the ball, timing, hand-eye coordination, and a good mental approach are all just as important. I know a very athletic kid with a picture-perfect swing who DD has been outperforming for years with her effective but less pretty swing.
He is late on an inside FB. And instead of pulling his hands in like Mike Trout does he releases his hands and is unable to get the barrel on the ball. The great hitters can make adjustments. He is not a great hitter.
My daughter played with a couple girls in the past that had great swing mechanics. Could flat out crush it during coached pitched BP. But faced with live pitching and it was all K's. Some batters just can't hit no matter how good their swing is.