The Geonim have all too famously written not to rely on the Gemarah for its medicine. Now, this is referring to the Sugyos in Shabbos and Gittin where it actually lists remedies for assorted ailments.
The Gemara mentions how Abaye tried one of them and it didn’t work. Eventually, an Arab merchant directed him to try something entirely different. This shows us a couple of things: That the remedies can change and that they aren’t necessarily from their Rebbeim but can be what they picked up. The Gemara records what Rebbe Yochanan was told by his doctor.
These were recorded because it was important enough to pass on. These haven’t made it into discussions of Torah/Halachah. In fact, Chazal never quote outside sources when deciding Halachah. You might find how they consulted a doctor at a particular moment to decide what something was, but not in order to establish an Halachah on the word of an outside influence.
The medicine Gemaros are an exception and don’t pay a role in Halacha. It is for this reason and about these Sugyos of which we are told ‘they were out teachers, not our doctors.’
The Chachomim didn’t shy from attributing their knowledge to their proper source. It is them who taught ‘he who says something in the name of its author brings salvation to the world.’ Yet we don’t find them attributing their ideas about the world to any outside thinkers. And quite the opposite, we find them quoting Braysos or deriving from them all matters of Halachic or Torah consequence. There are instances of Rav Popa deriving medical and anatomical information from Mishnayos and Braysos. He completely sidestepped the idea of referring to Galen.
This is what makes the Gemara timeless. Contrast this with Rishonim who, without that vast treasury of resources of early traditions, had to fall back on outside knowledge. And therefore, when that information of outside origin became obsolete so did the foundation based upon that. This leaves us scrambling to redefine or reapply those words of these Rishonim.
Just to be clear, this is not a claim that Chazal knew all the secrets of nature. In fact, if is clear from many areas, including those mentioned above, that they didn’t. However, what they learn from Braysos and Mishnayos is Torah and is true. We can actually learn from Chazal themselves how they viewed observed science vs. traditions and extrapolations of Torah.