Mycorrhizae penetrate into the root. The part that extends out into the soil is able to "digest" minerals that exist in your soil, that the roots cannot metabolize. The mycorrhizae then feed these minerals into the roots. This is not opinion, this is fact. However, if you don't believe that providing your plants with a higher diet of minerals that are present in your soil, grow them how you like.
I have had incredible results with stopping Blossom-End-Rot with a dose of calcium. Adding magnesium sulphate has given me results that were great. The magnesium supplementation has eliminated flower-dropping for me and, has provided a very noticeable increase in branching many times over the years. So, even though I've never used the Cal-Mag product, both of these elements have solved some pretty serious issues for me. Comparing the effects of myco to the benefits these two elements, would greatly encourage me to use myco in my soil.
Mycorrhizae will not only increase the amount of these two minerals to your roots, myco will provide your plants with an increase IN ALL MINERALS. As long as those minerals exist in your soil to begin with.
Mycorrhizae in your root zone, in effect, can have the effect of increasing your root-mass tens times over and, can metabolize stuff that your roots NEVER WILL. Yes, chlorine, chloromine, insecticides and harsh chemical fertilizers can kill myco.