Yes that's mostly true of Hinduism today, but only because 5 schools (of the 6 main ones) have diminished. The Vedanta school is prevalent today, and that one relies on Vedas (of which Upanishads are a part). But, for example, the Yoga school is fully empirical (i.e. first person experience) and doesn't rely on Vedas or any writings for its philosophy. Their teachings are mostly techniques or experiences of previous gurus to get to the stage of realizing the truths for oneself.
Yes that's mostly true of Hinduism today, but only because 5 schools (of the 6 main ones) have diminished. The Vedanta school is prevalent today, and that one relies on Vedas (of which Upanishads are a part). But, for example, the Yoga school is fully empirical (i.e. first person experience) and doesn't rely on Vedas or any writings for its philosophy. Their teachings are mostly techniques or experiences of previous gurus to get to the stage of realizing the truths for oneself.