Actually it does. There's a significant difference between listening to Spem In Alium on youtube after having been "enlightened" by modern culture and science, and walking into a Church hearing it performed live having only heard music on special occasions and fully believing in God since religion's power was as strong as science is today.
But you completely misunderstood what I was saying. What I was saying was that Mortiis is not classical, educated music like all of your "alternatives" to it (except justin bieber (seriously, how old are you?)). I was saying it would be laughed at by the common man in the same way that Burzum would be. You gave Burzum your suspension of disbelief, otherwise you would've just sneered at the ugliness and simplicity and turned it off like a normal person. And after you let it take you, you found that beneath the ugliness there was a strange, mysterious beauty, something lost deep within us. Mortiis is magic because it utilizes simple, primitive musical ideas to convey beauty within decay and darkness. It does it in a very similar way to black metal, except it is less warlike and more mystical. Classical church music and ancient folk music like your examples are wonderful, but they have existed for hundreds, even thousands of years. They were composed for a people living closer to the state of nature, closer to where our biological minds were meant to be. Black metal and Mortiis are music for sick souls yearning for something forgotten, something within us that has been destroyed by globalism and one ugly consumerist mono-culture. That something did not need to be recreated in ancient times because it was probably a normal, accepted part of life. And so art was simply something that was meant to complement certain events and activities such as church, or rituals, or festivals, or whatever. Now art exists to fill a void within us. The modern world is shit, but it's an unstoppable mountain of shit, so escaping to a beautiful fantasy that resonates with our spirit functions almost as a painkiller for people who are very sick from modernism (a disease to which we do not yet have a cure, and the search seems futile).
Beauty within a decayed primitive sound resonates with us because we are decayed primitive people (we all are, thanks to this modern world), but the best art suggests something powerful and unspeakable within, and I think Mortiis has that. It's like a mystery that we can never know the answer to, and yet it's beautiful because of that, because it suggests that even in the darkest times there's still something.... it's not hope, but it's something.