Last internship position I opened, I received more than 100 applications. Going through all of them and replying (even with a standard template) was grueling. I did give feedback to everyone we interviewed, though.

A good 50% of the resumes were flat out wrong for the position or missing critical information. A standard rejection letter with stats like these and basic recommendations might be useful in the future. It might also trigger a lot of self-righteous justification though... Don’t know if I’m up to receiving another 100 re-submissions with cooked CVs.