Well, that's exactly it, sad as that is. How many more recruiters are you going to hire to screen your candidates if the process you have currently does yield good candidates already. I'm not saying I agree with it, but I also don't have a good solution for the problem at hand - 1000+ applications for every junior role which all have to be looked at and filtered at least somewhat so you get a pool of people to actually interview.

A company could establish two separate streams for recruiting - aim to take 90% of candidates through the normal process, and the other 10% based on notable independent achievements/contributions. Still filtered, just differently. Not perfect, but might have interesting results.