Images Rejected - "Quality Issues"

First (Colosseum):

Out of focus, full of noise and artefacts.

Missing contrast.

The Histogram shows missing blacks:

Second: Distracting yellow blob in the foreground. Missing contrast due to counter light. Blown out whites (right), missing blacks (left):

I think, the focus should have been on the flowers and not on the background.

Third (sun): Missing blacks and shadows, missing highlights on the histogram:

As soon as you try to correct, you will get noise.

Fourth: you will need model releases from at least some people in the picture.

You have a soft focus and underexposed shadows.

Blown out highlights:

You need to edit out logos.

Fifth: underexposed shadows.

(left original, right corrected).

White balance to cool (blue).

I'll stop there. Some other issues, but not all, have been addressed by @Jill_C and @Test Screen Name .