Their recommendation system is really the heart of the beast. It's essentially a dopamine reward system, not too dissimilar from a slot machine at a casino. Pull the lever (refresh the page) and get random results! It sucks you in to a cycle of refreshing, finding videos you're interested in, clicking, rinse, repeat.
Personally I found myself losing hours per day to this behavior and gaining very little from it.
Far more productive, is going to YouTube for something SPECIFIC. Use the search function to find what you're looking for, and watch those videos, but never use the homepage or sidebar recommendations.
There are actually google chrome plugins which will totally remove the recommended section:
https://chrome.google.com/webstore/detail/unhook-remove-yout...