I don’t think Apple has every really had great backwards compatibility. Apple’s last PowerPC computers shipped in 2005, and in 2009 Snow Leopard released with no PowerPC support. That’s 4 years of upgrades, which is about the same as it is now for macOS.
Swift. Mostly because it’s by far what I’m most familiar with. Two things come to mind for what I most like about it. 1. Progressive disclosure: I found learning Swift to be simple since I didn’t have to directly concern myself with advanced features, but as I learned more I could take advantage of these more advanced features. 2. Clarity: I find Swift far more readable than most other languages. I think this is a combination of language features (argument labels for example) and consistency across the standard library and popular third party libraries. I think Swift finds a good middle ground between brevity and expressiveness; there’s never too much boilerplate to write, but the code is usually fairly self documenting.