I disagree and agree with your definition of Nirvana. It is the release from the cycle of death and rebirth but not in the physical sense. It's a freedom from those concepts of death and birth. Our entering into the physical plane was precipitated by our parents, their parents, and so on. An enormous amount of things had to happen before we were born in order for us to come into existence. Therefore we were born long before we were born physically. And we change the course of the world by coming into existence and it'll be forever different even after we cease to exist. It is a release from birth and death in the mental sense. A freedom from those ideas that limit human lives because we existed before our physical time on earth and will exist afterwards since our existence was written before we came physically and has changed the world's story such that it will be different after we leave physically and continue to have been changed because of our lives on earth.

And I do not believe Buddhism is a philosophy of negation. That to me is merely a tool, a way of thinking that helps to eliminate the dualistic thought that blinds people to the whole reality. It only denies those things to release people from the limited perspectives society has normalized. "Do not confuse the finger pointing to the moon, for the moon " Buddhism is a philosophy of understanding and acceptance in my opinion. An understanding we create our own realities based on our interpretations of life around us and acceptance of both the relative truths and ultimate truths that govern existence. It's this intimate understanding of both that allows us to be free from dualistic thought and make the most beneficial decision that contributes to our well being and that of the greater good. I do not believe calling Buddhism a philosophy of negation looks deeply enough into it imo.

But also I know Ultimately these are just the theories I subscribe to and that make sense to me