Screenshots of what you're doing.

With the new settings it looks better.

The stained glass is actually something i wanted to suggest to you but they don't seem to cast colored shadows :c (have to wait till rtx gets mainstream)

The windows look a bit too colorful imo. They should have an overall theme. I'd consider them as colorful detail but not adding to the contrast in general.
My naive advise:
Maybe take a step back and look at the whole picture. Be more daring with colors. And if you want realism, take materials that contrast and complement each other.
With contrast particular I meant the whole image (or any arbitrary taken from any angle and position in your map but as whole picture itself)
To me the rocks and the cathedral stone look to similar, not differentiable enough.
Maybe try making the rocks somewhat darker.

The roofs I'd make dark like from that old (before getting rid of the roof) photo of notre dome.

Also the random pattern of the cathedral bricks look odd. (and there im just niggling again ;P)
Nah srsly the guys who built cathedrals had a kinda perfectionistic mindset i'd say as they were building it for their greatest belief.
So it must look perfect in layout and placement. The rotten looks you can generate by foliage growing in between, cracks, notches, erosion, holes etc. Basaically look at how those stones erode over time.
Then the question is if someone maintains the buildings? Yes: candles lit; No: broken rocks inside etc.

Some ideas:
Don't know how much you want to go into detail but imagine the guys building your cathedral. You could tell little stories of how they built it and what they did there. Where they repaired stuff. Maybe a worker fell off the cliff and got his name engraved at the place. Some markings. Something that makes it seem like they were people involved.