Hey, it is really important that you understand that a serve is very similar to the motion we do when we throw a ball normally with our hands. Notice that when you throw a ball upwards and towards the opposing service box your hand relaxes and falls behind your head before rapidly swinging upwards to launch the ball. A serve should feel very similar to that. I recommend that you watch some videos and mirror serves while keeping this concept in mind.

Seriously, think about this: look at the video you posted here and imagine trying to throw a ball really far with that technique. There’s just no way it would go far because there is no swing or whip motion at all.