RSR,
Respectfully your argument is backwards in my opinion.
I listed multiple pistols I own with poly triggers. This isn't 1950's bakelite we are talking about. Most of these formulations of materials (such as glass filled nylon) can be far superior in wear (for the service and function they are design for) and tensile strength as compared to steel.
As far as generational longevity I promise that you can spray polymer fire arm parts with salt water every day and subject them to a widow and offspring ignoring them to 20 years without maintenance before touching or transferring them, and there wont be a speck of rust anywhere. My weapons collection in deep storage literally drips with MC3000. If they had polymer back in the 1800's you would have a lot more barrel-less civil war rifles today.
Heck - what about the EVO 3 - is that trigger polymer?
It's very possible that you're correct. Again, admittedly, it's something I get hung up on. That said, my firearms are much more likely to see deet and cleaning solvents that dissolve polymer than they ever are to see saltwater... And modern firearm coatings are far superior to the parkerization and bluing of rifles of old...
Though it's an entirely separate discussion/tangent I'm not going to pursue, but would like to mention that a lot of the requirements of military weapon systems today especially in regards to cost and weight minimization, and quick change barrels/calibers (but others too) are often not aligned with the needs of the consumer/civilian/sportsmen market... I'd be in hog heaven living exclusively with 1950s-1980s era weapon systems, provided I can give them modern outfits/upgrades... (Though I will admit that pistols have evolved significantly since that time and would prefer a modern production all metal pistol to one of that era.)