Yes, there are plenty of theoretical physicists pushing different types of "multiverse" theories for a variety of reasons. But existence claims about "other" universes necessarily involve philosophical questions that are not the exclusive province of theoretical physicists to address.
I tend to agree more with Hossenfelder (who has criticized current practice of theoretical physics rather broadly) than the likes of Carroll. Some theoretical physicists produce work that includes claims not amenable to experimental or observational test, and suggest that this means a need to redefine the scope of science. Critics argue that this is nonsense; rather, the work they're doing, in such instances, simply is not scientific. An example of such critiques is a Nature commentary by George Ellis and Joe Silk:
This year, debates in physics circles took a worrying turn. Faced with difficulties in applying fundamental theories to the observed Universe, some researchers called for a change in how theoretical physics is done. They began to argue — explicitly — that if a theory is sufficiently elegant and explanatory, it need not be tested experimentally, breaking with centuries of philosophical tradition of defining scientific knowledge as empirical. We disagree. As the philosopher of science Karl Popper argued: a theory must be falsifiable to be scientific.
...snip...
As we see it, theoretical physics risks becoming a no-man's-land between mathematics, physics and philosophy that does not truly meet the requirements of any.
There's an industry within theoretical physics that seems to serve mostly to generate flashy but dubious claims and direct attention away from the slowdown of experimentally predictions in recent decades in fields like particle physics. They are very smart people who have ideas worth considering, but as Hossenfelder points out in "
Lost in Math," they're working within a tradition that exalts mathematical "elegance" and "beauty" within theories - a tradition that served 20th century physics well up to the 1970s, but which has largely failed to deliver since.
So it's actually far from surprising to see a list of big names supporting this direction; to the contrary, the fact that so many brilliant people want to include speculative ideas that are likely beyond in-principle confirmation is evidence of the very problem Hossenfelder and other critics decry!
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