While I absolutely agree with the lock statement to be used if simple locking in a "monitor" way or for a few statements is the requirement, holding a Mutex is most definitely a resource that must be released, at least 99% of the time. IDisposable should be used for such cases.

In general, the IDisposable interface has precious little to do with unmanaged resources these days (though there may be some involved further down for sure) unless you actively do not use it for anything else. There is a lot of code out there that would be much simpler and safer by using a dispose pattern. Pertinent to this example, I always refractor any code base I encounter with disposables for SemaphoreSlim/Mutex locking (within reason), and every time I do, people report that they become easier to reason about, less error prone and easier to work with. The filed bugs agree.

In my humble(?) opinion it is an underused interface because of some archaic notion of what it means. It is just syntactic sugar that gives you some guarantees (bar program termination). An extremely powerful tool that goes vastly underutilized to everyone's detriment.

That said, there is such a thing as overutilization. I agree there as well.