The argument wasn’t that you need the joy of scientific discovery; it was that scientific discovery is important to us for reasons entirely apart from joy. You would never want a Soma substitute for scientific discovery, because that wouldn’t involve… you know… actual scientific discovery.
He makes good points, but note that there’s nothing saying you couldn’t take Soma and participate in the joy of scientific discovery (or whatever).
The argument wasn’t that you need the joy of scientific discovery; it was that scientific discovery is important to us for reasons entirely apart from joy. You would never want a Soma substitute for scientific discovery, because that wouldn’t involve… you know… actual scientific discovery.
Additionally, another different take on this is Yvain’s Are Wireheads Happy?.