We know too much now. What was ambitious in 1850 would merely be self-important in 2020.
Imagination, boldness, knowledge. Pick 2 of 3. Look uninspired, feeble, or clueless.
That position seems tantamount to saying we’ve reached the end of history. Isn’t diminishing returns part of all human endeavors? The more we know in aggregate, the less of the whole is made up of each new idea, but that doesn’t mean there are no big ideas left to uncover.