I would say packet slicing is one of the most critical techniques to understand.
Back in the day when we had hard drives with limited disk space and we needed to capture for long periods of time, we used packet slicing.
Today I use packet slicing for a slightly different situation. Sure, I might have a large drive but now the network speeds are much higher than 15 years ago. The other important reason why I use packet slicing is when the data is sensitive and we are not allowed to see the captured data. There are some other reasons covered in the video.
The point of the video is to introduce you to packet slicing but you should go look at your packet capture tool to determine if you have packet slicing and how to configure it.