Theoretically you can use channels to simulate a mutex, but I agree with you there are use cases where a mutex makes more sense. They are even used in the standard library, for instance to implement sync.Once.

But generally I would agree that if you need to code parallel execution, channels are a good way to do it, because you can avoid race conditions if you share data only over channels. The biggest problem is that a lot of people don't understand, that channels with a buffer larger than 1 are a sign of problems in the architecture.

There is a type of parallel programming with workers for specific functions, that always leads to performance issues. The problem is you need to right-guess the distribution of work, when you have to define the amount of workers for a specific function. At least one go routine for one request is a much better approach than function-specific workers.