The Rambam is pretty clear:
In More Nevuchim (3:14)
“Do not ask me to reconcile everything that they (i.e. Chazal) mentioned regarding astronomy with what is reality, for the sciences in those days were lacking, and they did not speak about them through traditions from the prophets, but rather on their own independent knowledge or what was obtained from contemporary scientists.”
Like was pointed out earlier, Rabbi Slifkin never says that his opponents views are not valid opinions.
In either case I never quite understood the argument that the Rambam is a daas yochid so we can’t Pasken like him.
We are talking about a Mitzius, if the mitzius is that he is correct (That Chazal’s science was based on that of the scientists of their times and was not given to them via the Mesorah) then it doesn’t matter who argued with him-because he was right!
The argument HAS to be about the proofs that exist for what scientists say vs the proofs to what Chazal say in scientific matters; Arguing that we can’t or don’t “Pasken” like someone is missing the point.