I understand this argument but I struggle with it.
For one, despite the human ego we actually know very little about our universe:
“The universe is not constrained by what some blobs of protoplasm on a tiny little planet can figure out, or test,” Siegfried says. “We can say, This is not testable, therefore it can’t be real—but that just means we don’t know how to test it. And maybe someday we’ll figure out how to test it, and maybe we won’t. But the universe can do whatever it wants.”
https://www.nationalgeographic.com/science/article/what-is-the-multiverse
... and that includes Brian Cox, one of my least favourite blobs of protoplasm
But we are able to look at other solar systems are there appear to be no shortage of both rocky exoplanets like Earth and gas giants like Jupiter:
"Already, too, we have a wealth of exoplanet data from observatories such as NASA's
Transiting Exoplanet Survey Satellite (TESS), the agency's retired
Kepler space telescope and the High-Accuracy Radial velocity Planet Searcher on the European Southern Observatory's 3.6-meter telescope at La Silla Observatory in Chile. NASA says more than
4,000 exoplanets have been found by early 2022, a large proportion of them gas giants."
https://www.space.com/30372-gas-giants.html
So it does seem that the requirement for an outer gas giant is likely to have been met in a great many of the 40 billion solar systems in our galaxy, which somewhat undermines what Morris is arguing.
But I feel my hesitancy also arises from the 'unique Earth' hypothesis being used within the climate change debate. I am not a climate change denier, but for those scientists and presenters who make their living from being in the public eye it is a gold mine. Brian Cox, for example, is able to garner headlines from stating he believes we are the only intelligent life in our galaxy, therefore it is an absolute tragedy if we allow ourselves to destroy our biosphere through man-made climate change because then the universe is losing something unique. This raise this profile, but him at the forefront of the climate change debate and more work will follow...