I myself have been on a mountain sacred to Quanyin, the boddhisatva of mercy and childbirth. We know for a fact this is a repurposed pre-Buddhist deity. The rites were definitely theistic in nature, so I agree that Buddhism has those elements. But Buddhism is such a diverse tradition, making any sweeping statement about it on anything is risky. The Buddha himself never taught about worshipping gods, only a path to escape suffering. So it is not inherently theistic. The theistic sects emerged because of merging with local religions (e.g. in Tibet and China). In non-theistic Buddhisms, the boddhisatvas and buddhas are regarded as enlightened humans who have achieved Nirvana, not gods in the classical sense. They rose up, rather than coming down, so to speak. So a lot depends on which particular sect or school of Buddhism you are looking at.