One other way you could say this would be:
All that effort was for nothing.
The Cambridge Dictionary defines for nothing as an idiom:
for nothing (idiom) with no good result or for no purpose
There are plenty of other ways to say it, though. You were on the right track:
- The time I spent scheduling was a waste.
- All that time I spent scheduling proved to be unnecessary.
If you want to quote Shakespeare, you could say:
All that time arranging interviews turned out to be much ado about nothing.
Much Ado about Nothing is the name of a Shakespearean play, although many use that phrase to indicate roughly what you're trying to convey. In that context, though, the ado seems to include not only a lot of expended effort, but a lot of fretting or arguing as well. So, if you were only trying to focus on the time lost, I'd use one of your other options. However, if you wanted to highlight not only the time you lost, but also how the whole experience drained you emotionally (scurrying to meet deadlines, fretting about your qualifications, high hopes for new employment, etc.), then it might be a rather good fit after all.