Something led me to the Lancia Appia page at Wikipedia, where this picture utterly captivated me. Look at how open and airy this little Appia Third Series (1959-1963) sedan is, and how accessible its front and rear seats are. All four door sedans should have been built like this.
Yes, I know suicide doors had/have certain iffy aspects, but they could have been mitigated, by special locks, or whatever. Possibly even by requiring the front door to be opened first. But there’s so much to be gained, especially in the smaller cars, where entry and exit from their short doors was not always idea. This just looks so…right.