Right. Sacraments "work" ex opere operato. It is their efficacy which varies according to the circumstance and the individual soul.
A schismatic priest can consecrate a true Eucharist and a schismatic can receive that Eucharist, .....
I don't think God is rushing around cutting off sacramental taps, so to speak.
The teaching of the Church Fathers and the Tradition is that God does cut off the sacramental taps...
Here is a patristic viewpoint from Saint Basil the Great. Notice the typical balance of the Church Fathers - while the principle of no Sacraments and no Apostolic Succession outside the Church is clearly enunciated, Saint Basil also states very clearly that for the sake of the good of the Church "economy" may be used if it is thought necessary in the case of Baptism.
Epistle to Amphilochius (of which the "First Canon" of Saint Basil is a shorter version)
---- "It seemed best to the ancients-I refer to Cyprian and our own Firmilian-to subject all of these-Cathari, and Encratites, and Hydroparastatae-to one vote of condemnation, because the beginning of this separation arose through schism, and those who had broken away from the Church no longer had in them the grace of the Holy Spirit, for the imparting of it failed because of the severance of continuity.
"For those who separated first had ordination from the Fathers, and through the imposition of their hands possessed the spiritual gift; but those who had been cut off, becoming laymen, possessed the power neither of baptizing nor of ordaining, being able no longer to impart to others the grace of the Holy Spirit from which they themselves had fallen away. Therefore they commanded those who had been baptized by them, as baptized by laymen, to come to the Church and be purified by the true baptism of the Church.
"But since on the whole it has seemed best to some of those in Asia that, by economy for the sake of the many, their baptism be accepted, let it be accepted."
Notice the word economy used here by Saint Basil with reference to situations when baptism is not insisted upon. Saint Athanasius also uses the word economy with reference to the reception of heretics.