> Java is a great language because it's boring [...] Types are assertions we make about the world
This is less of a mind-was-changed case and more just controversial, but... Checked Exceptions were a fundamentally good idea. They just needed some syntactic sugar to help redirect certain developers into less self-destructive ways of procrastinating on proper error handling.
In brief for non-Java folks: Checked Exceptions are a subset of all Exceptions. To throw them, they must be part of the function's type signature. To call that function, the caller code must make some kind of decision about what to do when that Checked Exception arrives. [0] It's basically another return type for the method, married with the conventions and flow-control features of Exceptions.
[0] Ex: Let it bubble up unimpeded, adding it to your own function signature; catch it and wrap it in your own exception with a type more appropriate to the layer of abstraction; catch it and log it; catch it and ignore it... Alas, many caught it and wrapped it in a generic RuntimeException.