Image Sharpness/Detail

If you are shooting jpegs the options for further software sharpening of  all or part of the image which will yield what you want are limited because the jpeg has thrown out the needed data and locked the image to a particular aesthetic algorithm.

In this best of all possible digital worlds recording images in raw at the maximum bit depth and biggest color space allows almost unlimited opportunities to massage the data. The 18mp sensor in your camera in no way restricts that nor do the kit lenses when used optimally.

Your images are fine but you have to consider issues like lighting and depth of field both when capturing the image and post processing if you want to emphasize sharpness/texture in all or part of the image. I am sure you realize there is no way or reason to to software sharpen/enhance texture in what is out of the plane of focus.

If you are already shooting raw then find more training videos about sharpening and texture enhancement and experimenting in a program that allows layering, optimally Photoshop. If you are processing on the typical laptop its monitor is a significant limitation because you can only judge what you see and you can only see what the laptop monitor shows. An external monitor plugged into the laptop can reveal a whole new world--it is easier to process images on a larger monitor than any laptop screen and even more so as monitor resolution increases.

Shooting the same jpeg on a higher megapixel sensor with a more expensive lens will yield only a marginal difference in the image compared to what it does to your credit card bill. Its a lot cheaper and in the long run more beneficial to hone processing skills than to buy "better" versions of existing gear.