If you have the sun in the background like this, it means the city is strongly backlit: contrast, shadows! (It also means sunset).

The sun is never this yellow, either white in daytime, or yellowish-orange-reddish at sunset.

The city skyline could have a more balanced composition. The shading on the bldgs is weird, they all look rounded. Unless that's what you wanted, bldgs have flat sides and those sides are more or less evenly lit: sharply for those we see at a small angle, dark for the others, they don't get sunlight (if sunset).

Pure greys are boring... the lit sides might take a warm hue, the shaded ones a cold hue.

Same for the cloud.

The escalator is just 2 thin lines, totally unreadable and boring.
Try to give it a strong perspective, maybe make it much wider and coming directly from the front, to get more depth.

Then, maybe some background, a very low horizon, other clouds, ...

Why not just try? You don't have to make it highly realist, just a little bit better, one thing at a time... ;)

Would be fun to see some more variety on houses - for example, along the lines of Starcastle album covers.