I urge everybody to read an article published in Dinei Israel by Hakham Yosef Faur, on the Legal Methodology of Tosafot.
The idea that changing circumstances can override Talmudic gezerot is Conservative Judaism. And yet, Tosafot engage in this on many matters, including clapping on Shabbos, mayim acharonim, cheese (Rabbeinu Tam permits the eating of cheese that is vegetarian and not made by Jews, on the grounds that the Talmudic gezera applies because of concerns over basar v’ chalav and treifot), and even wine (Haym Soloveitchik’s voluminous research on the wine trade documents this, and Rema’s teshuva giving a limud zechut to Moravian Jews to drink gentile wine) and the status of Christianity reflect an approach that is not what Hazal or the Rambam certainly stood for.
Mayim acharonim is a definite chiyuv, as attested to by Hazal themselves in Hullin 105.