> having to worry about Send and Sync and Pin and fighting with the borrow checker and all that fun stuff.

To be fair, the alternative to having to worry about Send/Sync/Pin is not "not worrying about Send/Sync/Pin". It's having to worry about correctly enforcing the constraints they describe on your own, without any kind of mechanical help. E.g., not moving data to another thread that shouldn't be and not accessing data from multiple threads that shouldn't be. This stuff is intrinsic.

In this sense the Rust mental model is simpler, because failing to uphold these constraints is no longer "your fault", it's Rust's fault.

I don't disagree; I was coming from Java most recently, and a lot of the equivalents of "Sync" and "Send" were just mental notes I was making myself, and I wasn't really used to it being encoded into the type system.