mettelus
Don't waste 4 hours trying to use all the "nifty tools and gadgets" we have to correct something that could as easily be done by 10 minutes of re-tracking.

That one really hits home. I have a student I work with that constantly wants us to work miracles with bad takes that could be so easily fixed by just doing it right. This same guy is always asking me why another guy's songs sound so much better than his. I show him the project which has very little in terms of effects and illustrate that the key was rock solid tracking that eliminates the need for a million fixes. 

Lots of answers to this, but the most recent is: keep the levels down.
I've started using K-12 metering with Izotope's Insight, and keeping the loudness at about -24 LUFS.
Everything got easier.

I know you asked for (at least implied) the _one_ most significant gadget/event/feature, but I only have the energy/initiative to narrow down to four.
 
1) The release of Cakewalk Pro Audio, meaning that I (and countless others) could go non-linear & non-analog, ditching the tape recorder and the smtpe striping and the splicing block. For better or worse? You decide!
 
2) The "Project 5" era, when Cakewalk tried to expand outside its box (and its comfort zone) into new audio technology areas. With the actual P5 program, I include all the RGC audio stuff that came with it, including those trusty synths that became, and are still, a mainstay of creativity for me .
 
3) The regular inclusion of different third-party plugins, even (maybe especially) the "demo" versions. CW introduced me to PSP Audio, for example, and Melodyne, and others, which are now part of my, er, "signature sound".
 
4) The people I've encountered in these CW forums and their advice, tips, insights, philosophizing and dust-ups. Goodness golly, what a treasure these posts are (Um, I don't have to include the Coffeehouse in this, do I?), what an influence on my mixing (and a lot of other more-or-less audio/music related topics)! [Swell the Max Steiner score.]

To get that pop country bass sound that almost sounds like just a constant strong bass tone, I used the phase rotator
in stardust vst then followed that with a limiter and slammed it all.
 
Seems to have got me closer.
 

bitman
To get that pop country bass sound that almost sounds like just a constant strong bass tone, I used the phase rotator
in stardust vst then followed that with a limiter and slammed it all.
 
Seems to have got me closer.
 

Man I'd love to hear that!!!!  Anything online to listen to?

Don't overlook some of the most simple/fundamental tools.
High-pass filters allow you to achieve great clarity and separation.
ie:  There's nothing meaningful in vocal or guitar tracks down in the sub-bass range.  Filtering that out leaves space for kick and bass... and yields greater clarity.
 
 

As a follow up to my own thread...first, thanks for all who contributed.  I literally made a list of things I need to try/do/get better at as a result of your suggestions.  Two HUGE things that have a made a big difference in my mixes as a direct result of ideas presented here are:
 
1)  Gain staging.  I thought I was doing it right the whole time using Satson Channel and Buss, but was still running way too hot into my master bus.  Fix...TURN THE FREAKING BUSES DOWN.  Solved.
 
2)  Dave Pensado video about M/S stuff, cleaning up low end, and sweetening the mix.  This video is incredible if you haven't seen it.
 
https://www.youtube.com/watch?v=jKnRRrER718
 
Cheers everyone!!!!
 

That's going to go against what you said earlier, but I find if I highpass the mix, like, heavily - it sounds more together, more pleasant and closer to a radio ready release.And I do that after I highpassed guitars, high pitched keyboards and made room for bass and drums to breathe down there.

It's more in general operation terms, but spending time to learn and set shortcut keys immensely sped up my workflow. Also, the five minutes I spent looking at a speed comping tutorial (for X3) have been the single best invested five minutes I've put in the program.
 
For the rest, I'll have to go with some of the obvious ones; highpassing a lot of stuff and parallel compression.

There are several aha moments - but in keeping with the OP's request.
 
- Begin "every mix track" (except Kick / Bass / or needed low freq) with a Hi-pass filter rolling off at least 60-80Hz and otherwise Flat Lined Eq.
 
Only adjust for slight eq sweetening and mix placement for individual tracks near the end of the project.