Car doors are carefully designed to sound much stronger than they actually are.

I believe this, as the doors sound better, however, the weight and thickness of the metal has absolutely reduced over the generations. My ’12 seemed to have much heavier doors than the 5th gen, and the 6th gen looks slimmer, more like the one used on my wife’s Crosstrek. (Also heavier/thicker feeling than in my Maverick, which has significantly larger doors, although it does seal more airtight feeling). The 4th gen actually had a slight clunk when closing, more like old and newer doors, while they rattle, they don’t have the impact or weight behind them when they close.

Pressing a fist on the door, the doors sound ‘thinner’ than the old ones. Press lightly with your hand and the newer doors seem to deflect more than the older models as well. There is no real way, without damaging/cutting the door, to measure the thickness of the metal, and these metrics are far from scientific, however, it is enough to convince me that the metal is a lighter gauge on newer models. If you’ve removed one of the hinges for some reason, they’re no longer a two-man job. you don’t even need the help of a floor jack to hold it yourself so you can put it back on. Amazing how metal forming can create a better crash result, using thinner metal, but the newer models are better in crash tests, thanks to the engineering of the internal supports.