Decent lens, but far from perfect...

I can't tell if it's high resolution or low resolution because the the subject has no fine detail (as I said, the text is too close to be a real test of the lens and sensor). It is definitely low acutance.

Look, ultimately this stuff may not matter that much to you. I know I get accused of being too theoretical sometimes. If you get the results you want, none of it may matter that much. However, if you aren't satisfied, it's worth isolating exactly why.

The complaint you make (that the image is not sharp, but does improve when processed) suggests decent resolution and a lack of acutance. If you have a lens that does not resolve well, you can't reclaim it in post-processing; the detail from the scene is simply not recorded. That's why high resolution lenses are sought after, particularly in the digital era.

There have been many, many tests of the 18-55 and the 35 f2, done by a variety of reputable sources. Neither lens is perfect (not even the best lenses are) and if you had complaints about corner softness on the 35 f2, of field curvature on the 18-55 wide open, or that the 18-55 was not so good at the long end, these would all be things that professional testers have found.

What professional testers have not found is that these lenses lack resolution, or are inferior to the Sigma 17-50 f2.8. That suggests you either have unusually poor copies, or a workflow issue.