I would have said the opposite. Channels are great on occasion, but half the time I see them used in places where a simple mutex would be much cleaner and easie

I would have said the opposite. Channels are great on occasion, but half the time I see them used in places where a simple mutex would be much cleaner and easier to read or where a mutex could be hidden from the user entirely but a channel is used instead and has to be exposed to the user. They each have their place. There are specific things in the sync package I see abused frequently, but I wouldn't call use of the sync package itself code smell.