Youtube doesn't have real competition because hosting video is much more expensive than text. That's why Google doesn't make individual reports about YouTube, it's most likely not profitable.

Very few people actively delete their accounts, but platform eventually die if they can't attract the next generation (young users). Less than 20% of the youth use Facebook for example, because they don't want to be in the same platform as their parents watching them, it will be a long painful day death. Same thing can happen to any platform.

At least they are honest about it.