Required content for platform tvOS simulator is missing. Please reinstall Xcode.

My internet connection is slow. I don't want to download 11 GB Xcode. Could someone help me?

Better find a good place where you can use broadband internet.
The recent Xcode works with tight communications with Apple's servers. You will meet many other messages and cannot run or distribute your app unless you do things in the right way.

Generally, installing Xcode through More Download pages may work in a little less stable communications environment, but you need to download 11GB Xcode and many more hidden components.