In my (far from zero) inbox is on the order of 100 new messages. Each of these is report on a student project that took tens of hours. More than a person-years work.
Some of it is powerpoint, some google/docs, some youtube videos, some excel/document, some word documents, some canva pages, some other things including links that I can't open.
Doing solid critique takes me the better part of an hour. My responses are due in much less than 100 hours.
I think that best that a GTD or inbox zero approach can possible due for me is to let me know early that I am going fail at this.
Knowing that now rather than moments before I actually fail is valuable.
I can decide whether to reduce that hour to five minutes and mark a few that are worth coming back to.
I can perhaps recruit help.
I might ask the other instructors how they deal with this, or warn the administrator that mine are going to be very late.
Or I might realize that while the grades are due in much less than a hundred hours, the critiques will be valuable even if they are month late.
I don't know what actually in going to happen, my realization of the problems is only minutes old. I haven't even made my morning hot chocolate (it is not a morning for protein shakes).
And even though I don't know what my email box or tracking system will look like an hour from now, it's already delivered great value despite probably showing up as an abject failure in my personal KPI's.
Todays' system hasn't failed me, it just takes the blame for some earlier mistakes in my life.