Im not a very good basketball player so take this for what it's worth. Looks like your a little flat footed, mostly standing tall, your defense stance is upright and narrow. Watch a good defender and you'll see the opposite, he's bent over, flat back, low on the ground with a wide stance like a squat and keep the offensive player btw his hips. You're standing straight and up and he's just going around you easily. That's not how you play good defense.
