@shortstories @CapitalB I'm not prepared to claim that all ancient medicine is legit. Far from it.
Moreover a lot of the context has been lost in translation. A good example of that is the doctrine of signatures. People think it means that if a leaf has a vaguely liver shape, then the plant must be good for the liver. In reality it's a mnemonic system. If you already know that a plant is good for xyz illness, then if you can also identify a feature of the plant that aligns with that, it makes it far easier to remember among the hundreds of other medicinal plants one needs to memorise. It also makes it far easier to teach that knowledge to the next generation. So, it's not always just a matter of ancient people having incorrect understanding, but about modern people missing the proper context of the knowledge and skills concerned (and no small degree of ignorant conceit).
Another thing to consider is that plants evolve over time, both through environmental pressures and through human cultivation. So what might have had a certain medical usage in ancient times, may or may not still hold true to the same extent today. Then there's the identification. Prior to Linnaeus there was no uniform way to identify a plant, nor to differentiate sub-species or local variations with much accuracy. Botanical science has come a long way since then.
The thing I'd caution about scientific validation though is that firstly, scientists typically only study one isolated molecule at a time. They mainly only study it in animal trials (eg. mice, rats, livestock, etc), which may or may not bear any relation to how it interacts with human physiology. Rarely do they account for the entourage effect, or make an effort to understand how growing cycle and growing conditions effect the concentration of properties. And most importantly, they only study plants which have commercial/financial value to the pharmaceuticals industry, which normally rules out gaining any credible information about things a regular person can harvest for free from underfoot in their own yard. So frankly I don't use scientific validation as a benchmark. It's a nice anecdote to corroborate the centuries of prior use, but the lack of scientific validation has little to no weight in my opinion.