One major difference is that Kotlin can tell you about nullability problems from simply analysing the method body, without going any further down the execution

One major difference is that Kotlin can tell you about nullability problems from simply analysing the method body, without going any further down the execution tree. this is a lot more reliable, and fast enough for real time IDE error reporting, than doing symbolic execution and diving into every method call to figure out all the possible paths. Same with Rust: it can determine multi threading issues from the surface layer, whereas in other languages in order to detect data races and contention you need some serious tracing analysis as well as doing a lot of runtime profiling.