You misread both Trent and Unitatis redingratio of Vatican II. Trent's anathemas do not say that those anathematized simply cannot be saved. It does say that they are in heresy and need to repent of it. Trent anathematized people on the basis of their beliefs, not on the basis of their "church membership."
Vatican II does not say that all non-Catholics are saved. It says that they can be saved even while not formal members of the visible Catholic Church. It turns on the distinction between those who knowingly persist in erroneous, heretical doctrine and those who adhere to a non-Catholic denomination without fully realizing the reasons why. Someone who has been misinformed about what Catholics teach and believe might adhere to a non-Catholic denomination because he believes Catholics teach something truly wrong when in fact they do not teach what he thinks they teach. He is not culpable for error in the same way that the 16th-Century Reformers might have been, especially after they were directly admonished as to what the Church does teach, in the decrees of Trent.
Moreover, mere formal membership in the Catholic Church does not guarantee salvation. Many Catholics could and probably will end up in Hell. Those who have had fuller exposure to the truth and do not live according to it are more culpable than those who through no fault of their own have never been exposed to Catholic teachings and believe, falsely instructed, that Catholics are pelagians or practice idolatry. Of course a person so instructed has a responsibility to check out whether the things he has been told about what Catholics believe are true or not. So those non-Catholics who engage in polemics on the internet about Catholics being pelagians or idolaters at least have been told these claims are not true. The ball is then in their court to find out who is right--the Catholics who say, no, we don't teach works-righteousness or magic or idolatry or the neo-Reformation anti-Catholic polemicists who continue to insist that Catholics to worship idols and believe in works-righteousness.
But the run-of-the-mill Evangelical Protestant who firmly believes in Jesus Christ as God incarnate and has never paid attention to whether the stuff he's been fed about Catholic errors is true or false, is not in the same category as someone who has deliberately and knowingly rejected the truth.
This is called invincible ignorance and it was allowed for already at the time of Trent and was explicitly formulated by 19thc Catholic official teaching. It was not simply invented at Vatican II but is the consistent teaching of the Church. Mere membership in the Catholic Church or not in the Catholic Church by itself does not save or damn. What counts is how one acts on the basis of what one knows and whether one has, knowing that the Catholic Church's claims are true, then deliberately and knowingly rejected them.
Would that seem confusing to you?
Yes it is confusing to Catholics as well as Protestants and pagans. The Catholic Church is now going through the greatest crisis since the time of St. Athanasius. Trent was an infallible council, it defined doctrine, and bound the faithful to it. The 'separated brethren' is just what you say it is, something that is 'in vogue' with Modernist Churchmen, some who are actively seeking to destroy the Church from within, others who are just willing pawns. (They won't succeed in the end though). Ecumenism is not a doctrine it is a policy, and a failed one at that.