Well said, Rick, as usual!
Roots need oxygen & moisture at the same time to function. When there is only moisture, (because particles are so small that they fit closely together with no air spaces between,) roots suffocate and rot (overwatering.) When there is only air, they shrivel and die. An ideal mix is one that is plenty of air in it while moist.
Whatever kind of soil or mix one has , NOT packing it tightly into the pot can help preserve tiny air spaces.
Vermiculite collapses when wet. I wouldn't use it for anything but starting seeds. Perlite would perform oppositely, and is a helpful addition for maintaining more oxygen within container soil.
A good soil is more about its' texture and particle size than the actual "ingredients" used. Over time, organic bits decompose into smaller bits, so even the "best" soil, if it has organic components, will need to be replaced when this happens. The speed at which this happens depends on many variables, but on average, about 1-3 years.
