My opinion: The original meaning of the term yoga is something like "union". I'm not going to dig up any references to support this, so take this for what you think it's worth, but in my estimation, modern yoga is derived from ideas that start to appear in India, China and the Middle East/Europe at least 2500 years ago.

To me, the common thread of these ideas is a perception of the unity of opposites, that opposite terms create each other, and that a true apprehension of the world comes from a recognition the world's (and of your own) essentially wordless and selfless nature.

Originally yoga would have been a specific practical system to achieve this true apprehension, and techniques of meditation and breath control are part of this system. Modern yoga promotes the physical aspect of yoga almost exclusively, but in a tradition like Sivananda, the physical exercises that people now think of as yoga retain what I believe was their original purpose as conditioning and preparation of the body for prolonged mediation. In my estimation, similar ideas in China became, among other things, Tai Chi, a moving meditation originally meant to achieve essentially the same goal of wordless and selfless existence.

So I guess to answer your question, it seems clear to me that the goal of the practice of yoga is to foster a selfless approach to life. Clearly modern yoga is not this, and you seem to be a bit skeptical of yoga, which is smart. So at the risk of bashing, maybe like everything, yoga becomes its own opposite. Without an appreciation of the middle way, of avoidance of extremes, which seems entirely missing from modern yoga, we get schools of yoga that might as well be mind control cults, schools that promote one man, always a man, to godhood and beyond, and encourage weak and needy people to use yoga to strengthen the self, not release it. I think yoga does have a middle way, and this is clearly bashing, but the Sivanandas and Bikrams and Iyengars of the world don't promote it, and I don't see much evidence of it in this sub.