No, universal acceptance is related to the election and occurs in the first months, especially in modern times since we have television and very broad communication means; it is not related to the magisterium! Therefore, it is clear that John XXIII and Paul VI have been accepted by the whole Church.
However, what you say about the circumstances of the council may be a good point, if you are able to provide clear information about it.
During Vatican II, the Church was made sin just like Our Lord in the Garden of olives. This is the reason why, for the first time, a solemn council did not include infallible teachings, but included errors: therefore it seemed that the Church defected, but actually it did not, because the teachings were not infallible in their content.
One cannot understand the situation of the Church by a mere dogmatic reasoning. You say that this situation is unprecedented, but it is easy to answer you that the sedevacantist thesis is also unprecedented, since it never happened that the Church be vacant for fifty years and more: it is utterly false to claim, for instance, that the Church has been vacant during the Great Schism (the true Pope was the Roman Pope). Above all, if you say that a pope who has been accepted by the whole Church has defected with all the Catholic hierarchy, it is also unprecedented. There was well and truly moral unanimity when the text on religious freedom was voted, with only 3% of dissent!
Regarding the circumstances of Vatican II, we are free to reject it. Your point concerning infallible safety is not relevant...