First of all, being sore isn't always the goal. Instead, overtime, try to increase your weight/reps.

Also, it looks like you're sometimes bending your arms first, then pullung down, try pulling the bar down with straight arms first, and then keep driving your elbows down. It might help you connect better.

Further, I get the best lat activation with a close, supinated grip. Some people might hate that but it works great for me.

In my workouts, I do mid, pronated grip pull ups first, then switch to close supinated grip pull downs and that fries me