I've had another read through Dignitatis Humanae and can not, in good conscience, see any flaw. The text seems to me a sublime example of humanity in a world degenerated into gnawing despair and despondency.
That is your opinion. It is not for one's conscience to accept or reject a teaching of the Church; rather, it should be accepted with a catholic faith. How many read-throughs are required to grasp and understand a document that was never taught as de fide by the Universal and the Extraordinary Magisterium. If there is a doctrine that has ever been taught that agrees with D.H. we shouldn't be debating it: all Catholics would be of one mind and heart. But that is not the case because there is some flaw that one can see in this declaration which another can't. A teaching that has been pronounced and declared by a General (ecumenical) Council of the Church should be completely
catholic, which nobody can find reasons to shoot holes in them. The Church has never taught that man is free to choose what religion he wants to arrive at the Truth he seeks which will lead him to God, and therefore salvation. The person who chooses the wrong religion will not find salvation. That is what has been taught always, everywhere and by all. If this were the case then D.H. should have been written accordingly.
What say you about this world that has degenerated into a condition you describe as desperate and despondent? What has brought about this condition? The degeneracy of humanity has been the norm since time immemorial, beginning with the first humans created by God, except during the period of time when the Catholic Church was at her heyday, the glorious years when she had complete rule of the world. One true religion leading all souls to God. But heretics since Simon Magus down to this age's Modernists have broken the law and shattered the peace and order created by God and which heretics will continue to do what they have in their hearts until the end of the time because the sworn enemy of God, Satan, never sleeps. But ultimately, w have the promise by Our Lady that in the end Her Immaculate Heart will triumph and there will be once more only one Faith, one Lord, and one Baptism, and men's hearts will see that there is only one Truth to choose from and that this Truth is what will set him free. That is what true religious freedom is.