I get where you’re coming from—those older brass and rubber parts really do seem to last forever. But I’ve actually had a bit of the opposite experience in some of my projects. The newer plastic flappers, especially the ones with silicone seals, have held up pretty well for me, even in rentals with heavy use. Maybe it’s just luck or maybe certain brands are better than others? I do think installation makes a difference too; if the chain’s too tight or the seat isn’t clean, even the best flapper can start leaking.
That said, I totally agree that some of the “upgrades” out there feel more like downgrades. Still, I don’t mind swapping out a $5 part every few years if it means less corrosion and easier installs. Guess it comes down to what headaches you’d rather avoid—constant little fixes or dealing with stuck bolts and mineral buildup down the line.