Yechiel, i am genuinely pained by your post. Not only because you have shown zero regard for divreihem hakedoshim of chazal, but uou are advocating a wholesale abandonment of the halacha against taking refuos on Shabbos. A gezera was made forbidding all kinds of refuah, whether they are medications or otherwise, due to a concern of grinding.
Like any takanah on Shabbos, the act is still assur even if it’s not common to do the melacha attached to it, such as swimming, even though it’s not common to forge rafts in our time, or any number of takanos.
Taking medication in general is assur on Shabbos. It is allowed when one is in severe pain, defined as wanting to lay down from it. A mild headache would not warrant permitting Tylenol, but a headache that makes you want to lay down would.
Re, bloodletting. Refuos change, tosfos says that all of the refuos mentioned in the gemara worked in their time, but the teva of people changed even in their time, and they no longer work. However bloodletting does have a practical medical application even nowadays, as it is used for certain conditions.
Learning shabbos with daf yomi has probably led you to believe these things, or hearing people talk about the halachos – you should learn them yourself. If you are unable to learn them from their respective sugyos in shas and poskim, there are wonderful English seforim which discuss them at length in great detail, including rabbi ribiat’s popular 39 melachos set.