That is one angle of it and from what I can see as justified an angle as there is. It made me think about some things and absolutely seems like something worthy of consideration.
However, that is one angle of it. Many other angles need to be considered. It is good and well to try to not burden others with your misery or make an effort to have a positive attitude. But it is for instance also important to not have to live in denial, to not have to be a fake and to feel accepted as the person you are.
In the end, I think this video takes some good basic advice and turns it into a one-dimensional extreme ideology, which frankly is scary and off-putting and depressing. Ah yes that is right. Faking happiness or feeling pressured to be happy can make people extremely depressed!
It really is a dumb video. But it has a point.
Personally, I have so far almost always found that I feel the best and am the best when I am not trying to be something pre-defined. There are exceptions, sometimes effort and aim helps. And sometimes you need to fake this or that. But if you need a simplistic general rule, be yourself so far strikes me as the best one.
But yep I think this video has point that "be yourself" shouldn't be understood as a general license to be a dick or wallow in misery.