This just goes back to the whole, "it's not REAL art unless it's fits into this narrow field of appreciation and high society." Art is art, whether it comes from a novice or a genius. There's just no way to differentiate art from non-art in an easy way with a blanket phrase or sentence that defines it all.
Similarly, who are we to say whether or not someone is a director just because they use Youtube instead of Vimeo. If you have something of exceptional quality and you want to highlight it, then Vimeo is the better place to do it. But if you're just experimenting with simple and basic projects, then Youtube is perfectly fine.
And is there really a point in one's career when one can "officially" become a director, if they aren't already, the first time you make a film? You might not be a good director. But being a "director" is a role one plays or chooses to play on a film: because they control the different departments and orchestrate the overall vision. A "Director" is not a title that only an official committee can give you, you just are one, because that's what you did on a film: whether you did a good job or not. Only if you want to get high profile jobs would you try to make it more "official" by joining the Director's Guild.
But I'm not really sure where you're coming from if you think people on youtube making videos, at least with a story, can't be called "Directors." What exactly would you call them then?
You could say Filmmaker, nothing wrong with that. But again, when does one arbitrarily get granted the status of "Director?" Do they have to do something specific? Be somewhere specific?