J.C. Ryle (in Light from Old Times) explains the theological and spiritual implications of the Roman Catholic mass:

Whatever men please to think or say, the Romish doctrine of the real presence, if pursued to its legitimate consequences, obscures every leading doctrine of the gospel, and damages and interferes with the whole system of Christ’s truth. Grant for a moment that the Lord’s Supper is a sacrifice, and not a sacrament—grant that every time the words of the consecration are used the natural body and blood of Christ are present on the communion table under the forms of bread and wine—grant that every one who eats that consecrated bread and drinks that consecrated wine does really eat and drink the natural body and blood of Christ—grant for a moment these things, and then see what momentous consequences result from these premises. You spoil the blessed doctrine of Christ’s finished work when He died on the cross. A sacrifice that needs to be repeated is not a perfect and complete thing. You spoil the priestly office of Christ. If there are priests that can offer an acceptable sacrifice to God besides Him, the great High Priest is robbed of His glory. You spoil the scriptural doctrine of the Christian ministry. You exalt sinful men into the position of mediators between God and man. You give to the sacramental elements of bread and wine an honour and veneration they were never meant to receive, and produce an idolatry to be abhorred of faithful Christians. Last, but not least, you overthrow the true doctrine of Christ’s human nature. If the body born of the Virgin Mary can be in more places than one at the same time, it is not a body like our own, and Jesus was not “the last Adam” in the truth of our nature.