There are a lot of important points of difference. Whether functions are introduced with an explicit keyword; how return types are marked; whether semicolons can be omitted at end of line; how types are named (and the overall system for describing algebraic types). Not to mention semantics around type inference (and whether it must be explicitly invoked with a `var` or `auto` etc.) and, again, algebraic types (what means of combination are possible?). And specifically with Rust you have the syntax required to make the borrow checker work. Oh, and then there are the implicit returns. Rust certainly didn't invent that (I seem to recall BASIC variants where you could assign to the current function name and then that value would be returned implicitly if control flow reached the end), but it reflects a major difference in philosophy.
... Which is really all to say: different people are focused on different details, at different levels.
> Whether functions are introduced with an explicit keyword; how return types are marked; whether semicolons can be omitted at end of line; how types are named (and the overall system for describing algebraic types).
Yes, these are all examples of things I always thought were generally considered small enough differences that nobody who was okay with how C++ or Rust or Swift did them would find the way one of the others did it a deal-breaker.
> ...Which is really all to say: different people are focused on different details, at different levels.
For sure!
> examples of things I always thought were generally considered small enough differences...
The thing is that they add up. Writing C or C++ is unpleasant enough for me that I've seriously thought about learning Rust just to have an alternative in that niche that actually has traction this time. (I wasn't under the impression that Swift — or Go, similarly — is intended to be quite as low-level. But maybe they are?)