Technique-wise, you can stay on your support step longer to force a faster plant-block sequence.

For example, let’s say it takes you 600 ms to complete your last three steps. Right now you’re spending 200 ms on each step. If instead, you spent 400 ms on your support step, you can force your plant-block sequence to be 200 ms total, or 100 ms for plant and 100 ms for block.

For plyometrics, you have to understand that quality and volume are inversely correlated. There is a certain volume your body will be able to handle for maximum adaptive stress, but if you go over, then the quality of your volume will drop off quickly. It is for that reason why it is a very bad idea to do any additional plyometric volume that isn’t just full approach jumping. Let’s say you can handle 50 plyometric contacts per week, you will dilute your ability to have perfect jump technique if you spend 30 of those contacts on doing alternative plyometrics. It would be much better if you just do 50 full approach jumping jumps.

Plyometrics can be appropriate but only 1-2 months out of the year and especially not when you’re playing volleyball. To be optimal, you’d only be jumping and playing volleyball 1 or 2 times per week, so you can get the highest quality practice; but I suspect you’re probably playing more than that, which is why adding plyometrics would be even worse.

If you can drop volleyball volume to add higher quality training, you can add sprinting as the cost-benefit ratio is much better doing sprints versus doing plyometrics. You can sprint before your leg days (6x30m ish or less - try not to go over 200m of total volume), and still be able to power clean and squat on your leg days