One could say something to the effect of "remember those few years where almost everything coming out of Sig was awful?"
The beauty of guns like Glock and the M&P is the fact that they have so little need for precision fitting and fine tuning. They are more mechanically simple by orders of magnitude because they did away with linked barrel systems, barrel bushings, leaf spring extractors and sear springs, as well as utilizing a slightly more effective magazine design and ramped barrels. Of all these things, I'd say the magazine is probably the main reason the modern plastic people poppers are so much more reliable. But the coil spring external extractor probably also has something to do with all that...
I don't know if it is just simplicity. Ruger P89s worked great - with a link. The Beretta 92 is super complicated, but probably one of the very best feeders out there.
I could see the argument that Glocks are a little too simple - too many functions combined onto one part.
Really, it is hard to think of a really problematic design that couldn't be fixed with a better magazine and feed ramp profile. Most autos since the '30s have worked pretty darn well - BHP, Tokarev, P-38, etc. "Modern reliability" seems to be more of a fable than a truth brought on by modern manufacturing. My Glock 19 wasn't unreliable, but it was less reliable than other, older guns I have owned.