I think this comes down to philosophy; do you want the compiler to just check that the program works for all the current parts, or to have the compiler make sure that the program will work for all the possible ways the interfaces can be used as described?
Basically, Rust makes you ensure that your code can actually do all the things it says it can do, not just the things it is currently doing. Personally, I find that very helpful; I would rather do the work up front than have to go back and fix a lot of things later as my code grows. This might be based on my experience designing and maintaining very long lived systems, where I wish I had been forced to do things correctly from the beginning.
I'd love if it were able to predict correctness of the program, but it can't (halting problem something). It can only approximate it and to be meaningful, it has to be pessimistic. Which is one more headache to casual developers.
Basically, Rust makes you ensure that your code can actually do all the things it says it can do, not just the things it is currently doing. Personally, I find that very helpful; I would rather do the work up front than have to go back and fix a lot of things later as my code grows. This might be based on my experience designing and maintaining very long lived systems, where I wish I had been forced to do things correctly from the beginning.