I am pro-SSPX. I converted to the Catholic Church through the SSPX and still attend Mass there from time to time, so I am not biased against them.
But, for confession and marriage to be valid requires jurisdiction. The bide and Groom do administer the sacrament to each other, but they must do this according to Church law or it is invalid; and Church law requires that the minister have juridiction. It is the same with confession: It requires jurisdiction.
As one person said, there is an exception to this when there are extraordinary circumstances. For example, when you are in the great apostasy (such as we are today) when virtually every Priest is a heretic, or at least very tainted by Liberalism, the Church supplies jurisdiction. For example if two people want to get married, but they are on a desert Island or somewhere else where there will not be a Preist for more than 2 months, they can actually marry themselves without any Priest or witnesses. It is the exception to the rule.
In our day, when the bishops and Priest (and Popes - thinking of Assisi and “the old covenant was never revoked by God”) are leading the faithful into perdition, there is no question that a person is justified in attending a Mass where the sacraments are administered with the proper respect and devotion that they should be, and where the sermons are perfectly orthodox, as is the case with the SSPX…
Since we are in extraordinary times, I believe that the SSPX Preist have supplied jurisdiction, just as St. Athanasius, the objectively schismatic and excommunicated bishop did during the Arian Crisis. St. Athanasius - “The Cahmpion of Othodoxy” - had been banned from his diocese and excommunicated by the Pope, yet continued to act as a Priest. In the end he was proven right for holding fast to what the Church had always taught, and surely he had supplied jurisdiction, just as the SSPX does today. The difference is that we live in a time that is far worse than the Arian crisis.
So, in normal times the sacraments of confession and Matrimony would be invalid if administered by a Priest in the situation that the SSPX is in, but during our present crisis it is another story.