YouTube intentionally makes it easy for you to fall into a rabbit hole watching videos. Sure, you came to watch one cute puppy video, but 5 hours later you're still clicking through them because man, puppies are cute and it would be a tragedy to miss out on the perfect video.
If you've got a ton of time to kill, that's great. If you don't, now there's a new site you can use called Tube.
Essentially a minimalistic version of YouTube, the site allows you to search for what you're looking for and play it, without that huge sidebar showing up with all the things you could have selected and might decide to watch next or a comments section to suck you in. It also doesn't display any of the usual comments or channel advertisements throughout the entire page.
It's just your video.
When a video ends, it also just ends. You still have the suggestions for other videos to watch at the end of the video, so you still could end up watching those puppies for hours and hours, but you have to work a little harder for the distraction now.