Youtube is part of a larger company that makes money in various ways and does profit a lot despite the high costs of youtube. Its existence serves a purpose to google, otherwise they would have already extinguished it or changed the way it operates. To see if its sustainable or not you need to look broadly into the system in which youtube is inserted.

yeah except idc, google can go fuck themselves. if yt dies, there are other platforms, such as peer tube. not as big, but if yt goes to shit, that where the creators will most likely go