Do not take everything in the Chant at face value. Just as with the Dalish legends, some aspects of it may be true, such as the Maker being the origin of Creation, but much may have been altered even from what Andraste actually said. If you read the notes accompanying the bits of the Chant contained in World of Thedas 2, it is clear that it was originally an oral tradition and that many parts of it actually seem to bear strong resemblance to earlier folk tales both human and elven.
The Golden City may have originated in the Fade or it could be a reflection in the Fade of a city in the real world. If this was the case, because the city was originally golden, so long as no one actually went there, it would reflect their belief that it remained Golden. The old gods were said to have spoken to the Magisters from the Fade, urging them on. They were hardly likely to admit that what they were aiming for was really already black and corrupted. Once the Magisters opened their portal to wherever the city was, they discovered the truth, released the corruption and became corrupted themselves. The reflection of the city in the Fade would now match their experience of it.
There is a strong hint in Trespasser that the taint may not have been caused by the Magisters entering the Golden City but they merely released it. There is an account of the elves discovering something in the Deep Roads and sealing it away lest it destroy the world. The inside of the Titan in the Descent resembles a great city, not golden exactly but certainly bright and shining with lyrium, which as you know gives off a song. Mythal was said to have conquered a Titan and the codex about this precedes the one about collapsing and sealing off the entrance to the Deep Roads. If conquering the Titan was the war that Solas spoke of that started the Evanuris on the road to godhood, then it is possible the elves used the conquered Titan to create a magical city underground, using its blood (lyrium). May be eventually the drain on it was too much and it died and this lead to the corruption that turned the city black. The seals the elves created were sound enough until the Magisters sought to enter the city in the Fade. This instead gave them a portal into the original city underground and once there they were able to open the seals.
Alternatively the elves created a city, the Fade part of which was left in tact when Solas raised the Veil. The city was originally constructed of pure lyrium, which made it glow and sing. The elves believed the Golden City to be the seat of their gods, just as the humans believed it the home of theirs. The portal to where Solas trapped the Evanuris may well be within the Golden City. The huge blood sacrifice that it took to reach the city in the Fade corrupted the lyrium that it was made with and turned it black and the backlash corrupted the Magisters. Obviously in this version they are responsible for creating the taint.
What I don't believe in is the Chantry version that has the Golden City being the seat of the Maker and the taint being his punishment of all mankind for the sin of just a small section of them. The Maker may well exist as a first cause but I think much of the rest of the Chant is just fanciful. There are just too many things in the world, elves, dwarves and titans, which according to the Chant the Maker did not create and yet pre-date any evidence of humans in the world.
One of the annoying things with Solas is that you can never ask about really important things like is the Maker real, was there ever a Golden City, why did it turn black? As someone who claims to know so much from history, and has a particular knowledge of the Fade, that would have been really helpful. I'm pretty certain the thing he wouldn't tell you when you asked, which is the question why does the current world have to die, was likely because now red lyrium is also on the surface we are all doomed. The only way to rectify this is to wipe the slate clean and begin again.
In World of Thedas 1 we are told that lyrium is simply a mineral but now we are told it is the blood of Titans and organic. WoT1 also said the Chantry believe lyrium is the essence of all creation and some even call its song the voice of the Maker. Well that either makes the Titans closely related to the Maker or that part is wrong. However, the fact that red lyrium can grow from practically anything, even small organic creatures in the earth, means that nothing is safe from its spread. It is interesting that no one seems to have realised that sinking the Tevinter ship leaving the Storm Coast with red lyrium means the stuff is now also at the bottom of the sea and infecting marine life.
So stopping Solas and preventing the spread of red lyrium are likely to go together.