My '17 with 48k miles still makes a nice thud when I close a door. I don't know if they did change something, but I also don't know why they'd fix something that doesn't seem to be broken.
Not sure since I haven't interacted with a 2021 model but the Gen 4 is general has better sounding doors than the Gen 3 which were tinny and the sheetmetal vibrates. I have noticed that the 2018 Prime's doors feel a bit heftier than our 2016's doors. (It also has a rubber piece between the front and rear doors for noise reduction that our 2016 doesn't have).
Yeah, I have noticed that on my PiP since I got it, if the door is closed anything more than very gently. Kind of annoying as it makes it feel cheap, when the car is otherwise built very well. Ah well, wasn’t such a big deal that it was going to stop me from buying the car anyway.
There were several costs cut on the Gen 3, not that the Gen 2 was luxurious by any means but the lack of door pockets (Toyota claimed it was for sound deadening), the removal of shelves inside both glove boxes and the removal of felt lining on the lower glovebox made the Gen 3 feel a bit less compared to the Gen 2. That said, there were improvements like covering exposed screw heads and a nicer interior door panel (even if the door armrest is low for taller front occupants)
