"It takes like 1.5 seconds from the gesture starts until a window on the target space gains focus."

It's even worse than that. If you don't lift your finger from the touchpad, the gesture never gets to the target space, no matter how long you wait. E.g. if you want to scroll something in the target space with the 2-finger scroll gesture, but your fingers touch down before the space-switching animation had fully finished, then the content in the target space won't receive the scroll gesture, no matter how long you wait. Your fingers must touch down after the - very gentle and slow - animation has fully played out.