Since Google bought YouTube, the website is slowly but surely losing its soul. They destroyed channel customization. I guess many young YouTubers aren't aware that in the old good days we were able to customize the looks of our channels. A few times they destroyed the commenting system and still haven't fixed it. They're promoting the most controversial and often stupid comments, not the best. Many of the valid comments are lost by going to the spam folder. They have the worst spam filter I've ever seen. When the users organized a protest across the whole site, they were called "trolls" by one of the YouTube bosses (some Indian guy, can't remember his name). He believed the commenting system is great and the users are simply stupid trolls. If someone like this is in charge of things, you know things won't be well.
YouTube is now biased and have a strong censorship. They remove videos of users if there's something they don't like. They even remove their own videos if there are too many dislikes, or comments on their videos if they are unfavorable. Their video presenting the new commenting system is long gone. They recently released the video #ProudToBe: Coming Together to Celebrate Identity. 90% of the comments were unfavorable and they were removing them as quickly as they could. When they realized it's impossible to stop the negative tone, they simply disabled commenting, removing all the comments.
YouTube is also removing videos for nothing, sometimes banning whole channels with it. It happened to me as well. They incorrectly removed few of my videos and this caused a ban on my channel. I was lucky to appeal this and get my channel back. But imagine if I wasn't able to do this. My whole work would have been thrown to trash! Once they removed my video because it had relevant tags in the description! And it was against their new policy, even though the video was uploaded many years ago. I tried to appeal a few times, but they said no. All they did is send me this stupid video. Probably the most hated video ever, but they obviously disabled comments and ratings.
YouTube also has a horrible support. If you're lucky to make a contact with them, they most likely won't help you anyway. They simply don't care.
Recently it has been proven that Google is cheating their systems to support Hillary Clinton in the following election: proof. They are also doing it on YouTube by manipulating views and likes.
I must also mention the integration with Google Plus, which almost everyone hated. They were forcing YouTube users to use Google Plus. When this video went viral, they manipulated its views to something like one million only. I guess the only reason they didn't remove it is because Emma Blackery is too popular.
Technically YouTube is of course becoming better, but it all doesn't matter in face of the bias, manipulation, censorship and lack of respect for its own users.
But is YouTube in any danger? No. Not even close. They're actually growing. The reason is simple: no competition. Both Vimeo and Dailymotion are horrible websites. And if a serious competition is ever to be started, I believe this is the moment. You would need a capital of hundreds of millions of dollars though.