Time isn’t the only factor, water may not be available, if it’s a colder place, you need to keep it heated all day while you work. Dry bonded concrete works, if you’re replacing all the posts, it doesn’t sound like it’s only because a few failed, because you would just replace those ones. It’s not an inherently wrong job just because you don’t like it lol.

And auger makes the task moot anyways, and if it’s powder, a shovel works fine too.