The Quran immoral because because of the messages it conveys. The only way we can really say the people who wrote it were immoral is by inferring it from the work itself.

There are many times where the work / product / art stands on its own, and should you not know anything about the author, could not possibly be called immoral on its own merit. Admiring work like this, need not automatically validate the evil of the artist.

Just because you acknowledge that some aspect of something otherwise evil is good does not mean have to automatically excuse the bad, however you can recognise the good thing for just being good, on its own. You happily benefit from the work of shitty people, probably daily, it might even save your life one day.

Losing your appreciation for “something good” because of who made it is a perfectly reasonable take. But so is “something good” is good despite who made it.

Side note, genuinely wondering, is the Taj Mahal that intertwined with islam where we would not have it without? At the end of the day it is a tomb, and as far as I understand the biggest reason for it being built is love for the emperors wife