>The use of IEnumerable as a "generator" mechanic is quite a good hack though.

Is that a hack? Is that not just exactly what IEnumerable and IEnumerator were built to do?

It feels hacky because you have to (had to?) use it as the async/await tool and because of that the types you're generating and how they are handled is a huge mess.

Really you're generating the vague concept of a yield instruction but you can return other coroutines that are implicitly run and nest your execution... Because of this you can't wait less than a frame so things are often needlessly complicated and slow.

It's like using a key to jam a door shut. Sure a key is for keeping doors closed but...