I take your points on the feasability of it. I'd distinguish, though, between the theory and the practice. In practice, transhumanism might be a cult that serves the big tech industry, a kind of propaganda sustaining consumerism and the worship of technology.

But the concept of transhumanism seems to me implicit in the modern metanarrative. We're talking here about the ultimate end of modern (secular, liberal, humanistic) progress. Whether one piece of technology might prove counterproductive or futile is beside the point. What lies at the end of the "progress" we're on? Arguably, if we're being optimistic and we assume we'll muddle our way through, it's something like transhumanism, as Yuval Harari argues in Homo Deus. Pessimistically, we'd be looking at a postapocalypse.