I have been arguing for years that the primary cause of the crisis in the Church is an Eucharistic crisis. Disbelief in the Real Presence has real consequences. The heresy of the neumatic presence of Christ has been worming its way through the Church for decades.
Consider why we are even having this "debate" involving the distribution of Holy Communion to those who live in habitual sin, adultery.
This debate is only possible because of a massive collapse in belief in the Real Presence.
The following is but one example of this denial of the Real Presence.
No further commentary is necessary. The denial of the Real Presence is the grave sin that strikes at the heart of the Catholic Church:
The priest prays the Eucharistic prayer of blessing over the bread and wine (over us gathered) and through the power of the Spirit, changes them (us) into the body and blood of Jesus Christ - a wonderful gift to offer to the Father.