Good point by Richie Monroe. Itis not only the quantity of notes but the frequencies being filled that can cause muddiness and take away from the direction and movement in the music.
If you consider a composer such as Igor Stravinsky, for instance. Some of the writing is very dense with counter rhythms flying but the writing was so brilliantly conceived that there is room for everything. You know this because you can hear everything and it never is too much or too little, it is always just right.
Acheiving something approaching such a level of integration and flow in pop music is what makes the pros and top producers so great.
It is constantly the quest and as I record, arrange, write, engineer and mix more and more, I begin to pay more attention to these types of issues and the music and recordings improve exponentially as a result.
The point is, there is not one piece of equipment, mic, reverb, DAW, computer, keyboard, amp, speaker whatever that can improve my productions. They can improve a sound or add a different sound but, if I want better productions, I must grapple with the fine tuning of the arrangements. This is infinitely more difficult than learning the correct setting for a compressor or deciding which pre-amp you think is best.
These are the issues that will make the difference and all of us should take a good hard look at the work we do and ask ourselves if we are improving in the way we map out our productions so that the parts work better together, the frequencies are well balanced, the timing and execution of the parts is properly done, the levels and panning are properly balanced and the overall dynamic is correct.
I truly believe that by mastering such things, we can extract the most from our equipment and the particular nuances between the various brands becomes less important.