TF2 Edit nerd here;
totally agree with Tob's points on pacing/clip quality.
Also, one big reason that klm's edit is hard to follow is that there's zero sound effects. I didn't mind the visual effects in isolation but that + no killfeed + no sounds means it's often hard to tell IMMEDIATELY when he actually hits an arrow on someone or not. (The arrow impact sound is so satisfying, how could you not include that?) For reference, here's a fucking CRAZY tf2 edit where shit is all over the screen but you can still follow what's going on (shockingly) because of the sound cues: https://www.youtube.com/watch?v=29zYMnO8l00 -- you may not be able to follow aim very well, a style which some people will always inherently hate (for reasons I empathize with), but you always know instantly when an enemy dies.
In the klm/slicerouge edit, yeah I can still technically tell what is going on in the offending clips by squinting, thinking about it, or waiting for the follow-up smooth to tell me if he hit that arrow, but making the viewer have to exert effort to figure out what is happening isn't really what you want in an edit.
That being said, I don't think klm's edit is bad, it just doesn't really live up to its potential.
...holy fuck I spent an hour on this, I need to end this nerd essay before it becomes a 10-page paper on the history of tf2 editing. Don't do Film majors in college kids.