You seem to be mixing up sacraments generally, with the ordered ends of specific sacraments.

Of course the purpose of all the sacraments is to confer grace. In that sense, matrimony will ordinarily result in the sanctification of both spouses (according to a correct disposition).

However, the ends God intended for each sacrament are more specific than the general conferring of the graces unique to them.

Summa Theologica (Supplement)

Chapter 41 (Matrimony)
Article 1

"...in this way matrimony is natural, because natural reason inclines thereto in two ways. First, in relation to the principal end of matrimony, namely the good of the offspring. For nature intends not only the begetting of offspring, but also its education and development until it reach the perfect state of man as man, and that is the state of virtue...

Chapter 49 (Marriage Goods)
Article 2

"Offspring signifies not only the begetting of children, but also their education, to which as its end is directed the entire communion of works that exists between man and wife as united in marriage, since parents naturally “lay up” for their “children” (2 Cor.12:14); so that the offspring like a principal end includes another, as it were, secondary end."

St Thomas seems pretty clear that the procreation and rearing/education of children are the principal end of Marriage.

The Church has always taught that voluntary celibacy is the best state for sanctification, not Marriage. This is a hard teaching for many, but it is the truth.

That does not mean that if you are married, you can't be holy, of course, but Marriage has a specific purpose attached to it. The formation of a family.

This is one of the main VII errors, displacing the primary means of marriage, from procreation of children, to "love" and companionship of the spouses.

A new one  ...  Another one .... Welcome
But please learn to read.
In the citation from Chapter 41, St. Thomas says that that the principal end of matrimony is NOT ONLY the begetting of offspring, BUT ALSO reaching PERFECTION, or that STATE OF VIRTUE, in other words, we must be purified, illuminated, and sanctified through the Holy Sacraments.
We must cooperate with God so that we and our children will reach the state of perfection through the school (education) of penance, study,  daily chores, prayer, and union with God.

Nobody has argued against the ideal that sanctified parents are going to more easily pass on the Faith and raise sanctified children.

The 'learn to read' quip can apply both  ways - St Thomas nowhere states the sanctification of the SPOUSES is the primary end of Marriage. He places the begetting of OFFSPRING and the OFFSPRING'S attainment of virtue as the primary end.

Again, to reiterate, holy parents will more easily rear virtue in their children. But you have to have children before they can attain virtue and reach Heaven.

Where have you been? There are many Dominican Saints. One of the most recent is a Spanish Dominican widow who was declared to be a saint not too long ago. St. Catherine of Siena is also a Dominican Tertiary.

Isn't it a sin to render to God the bare minimum?

But why is this? Is not a man obliged to do the greater good? I say that one must distinguish the greater good in regard to the actual performance or in regard to the desire. One is not held to the greater good in regard to their actual performance, but to the desire to do them, because every rule and every action is determined to something defined and certain : but if one is bound to do every action that is better, one is bound to something uncertain. Hence, in regard to exterior actions, because one is not bound to do something uncertain, one is not bound to do the greater good; but in regard to the desire, one is held to desire the greater good. Hence, he who does not always wish to be better, cannot wish without contempt [of doing the greater good].⁵

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5. “There is a way of fulfilling this precept, so as to avoid sin, namely, if one do what one can as required by the conditions of one’s state of life: provided there be no contempt of doing better things, which contempt sets the mind against spiritual progress” (II II, q. 186, a. 2 ad 2um).