It is true that you would get more benefits from Wing as you write more of your code in it and give the compiler more visibility into your code. But you are not required to write everything in Wing, and there is interop to other languages. Since the language compiles to TF and JS at the moment, you can import JS libraries to use in your code and take advantage of the huge JS ecosystem.
The cloud simulator is not meant to simulate the cloud, including its non-functional concerns - you have local stack for that indeed. The idea of the simulator is to give you the most light weight and fastest way to test the functional aspects of your code while you develop it. You definitely need to further test it with local stack and/or the cloud.