Nope, its not profitable. Infact, like the sun its dilated the advertising dollar, which means not only traditional TV mediums are loosing viewers to, they are loosing value per advertising minute sold.
Its also not eating traditional TV. You don't sit down to watch a series on youtube. There is no such thing as longform youtube. There are no profitable 30minute episodic videos on youtube that aren't pirated.
Content is king, and if you are producing shit content (cough 90% of the US TV market) saturated with adverts and repetition, users don't turn to youtube, they turn to netflix.
Netflix will eat all, Youtube is, and unless something changes (like no user uploads) will always be a subsidised media charity store.
Yes, its cornered the MTV music video and nutshot compilation market. It has enabled niche video makers for things like hobbies and such. but there is literally no money in that either.