Interesting! IMO there are at least three seperate issues: 1. Quality of recording equipment and tracking skills, 2. Technical mixing and 3. Getting a certain "sound". They're all somewhat related, too.
Nr.1: The multitrack. Put a vocalist in a good sounding room in front of a well-maintained U47 and a Neve preamp through an LA2A with a little GR into a quality converter and you'll get a signal that works great and requires little tweaking, but will take lot's of it no problem, too. Similar signal chains and environments are being used and have been used for recordings for many decades, but it's not what in today's reality is availible to most. You simply need a lot less of 2. and will have much less trouble going for 3. this way, too.
Nr. 2: The technical aspect. It's what you're aiming at mostly, I think. Most people have less than ideal monitoring, an untreated room with budget monitoring fed by budget converters make it almost impossible to achieve balance and even hear the details necessary.
Nr.3: The "sound". This is where the high end gear helps again, to create excitement, texture, punch, debt and whatnot. The mojo, vibe etc. It's also the mixing engineer doing part of the producer's job by creatively using all the tools at hand. So it's inspiration, creativity on the one hand and the right tools on the other. What is technically right might not be the best choice after all. Walking the thin line between "wrong" and what is "inspired" is especially challenging, and knowing how to get the sound you want can be very difficult, too, and requires much, much experience. And, again the raw material must allow for this and often expensive gear is required to pull something off convincingly.
So in the case of the mix contest we're dealing with far from great sounding raw tracks, very probably lot's of non-pro's with little experience in less than ideal mixing situations and without mojo gear. It shouldn't surprise anyone that we didn't end up with a ton of jaw-dropping sounding mixes, and that in fact most of the focus was on getting creative with what was availible to each mixer. E.g., it might be impossible to get the low end right, but clever automation of delay lines and making up extra harmonies is availible to anyone now. If you look at current pop music that's exactly where it all went, using the DAWs endless possibilities for gimmicks to gloss over all the shortfalls of modern low budget recording, and semi-pro composition, production, mixing. All the way to the best-selling artists. I've got the tracklist for a recent Pink song: Ten different kick drums, 20 snare, hihat, cymbal, tambourine and shaker tracks, around 20 each for guitar and vocals, and lot's for FX, synths, bass and other things. And detailed instructions for a myriad of sidechain compressors, automation, FX, all done within the DAW.