Generally speaking, of course...
I think the challenge is that fast playing on low tuned instruments doesn't translate very well to many listening environments. Modern metal mixes tend to have a lot of high end and not very much bass. It's a challenge to get every note heard in every mixing environment without mixing this way.
Also, most modern metal records are obsessed with using the same guitar sounds, the same drums, etc. on each song. Consistency is nice, easy with software, but I don't think that more audiophile-friendly, analog-based bands like Pink Floyd and Led Zeppelin were worried about having the same kick drum or the same guitar sound on every song.
To have a deeper mix, I think you have to have a deeper album in terms of music as well. This isn't a knock to metal, but to me a great metal record like "Wages of Sin" isn't trying to communicate the depth of something like "Dark Side of the Moon" or "Led Zeppelin III." Many modern metal bands are focused on creating a consistent level of heaviness, shredding, great riffs, no "gay" songs etc., without much space or dynamics. Opeth is one of the obvious shining exceptions to that - and they don't care if you call them "gay."
As a mix engineer or audiophile it's easy to start looking at music scientifically, but at the end of the day it really comes down to making the production fit the music itself. Lamb Of God or Arch Enemy wouldn't sound right with a bunch of arbitrary "dynamics" or a really big sounding kick drum, or running the guitars through a vintage Supro combo instead of a high gain tube stack, etc.