Hi dguerriero,
Too much memory foam (or any softer comfort layers) can certainly allow the heavier parts of your body to sink down too far and put you out of alignment over the course of the night which can lead to lower back discomfort or pain but the opposite is also true that comfort layers that are too thin or firm can also create pressure issues and in some cases cause alignment issues as well. The key is always to find the “right” combination of layers and components that is the best “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
There is more about the relationship between primary support, secondary support, and pressure relief in post #4 here and there is more about “a perfect mattress” relative to each person in post #4 here.
Phoenix