Breathing practices objectively have an effect on our body and nobody can counter this.
Buddhist ideology on the other hand is up to debate and everyone is free to try it or believe it.
Maybe in your experience meditation is enhanced by believing all that stuff, but that is your prerogative. I can do mindfulness and go to a psychologist instead of doing meditation and going to a temple because maybe that oriental stuff feels too alien and doesn't seem right to me.
Buddhist ideology on the other hand is up to debate and everyone is free to try it or believe it.
Maybe in your experience meditation is enhanced by believing all that stuff, but that is your prerogative. I can do mindfulness and go to a psychologist instead of doing meditation and going to a temple because maybe that oriental stuff feels too alien and doesn't seem right to me.