Sharpness is measured in line pairs / mm (lpm), i.e., the number of line pairs / mm your camera and lens can potentially resolve. The higher the sensor mp, the more line pairs / mm it is capable of resolving. Glass is not perfect so sharpness varies in any given lens, usually dropping off the further you get away from the center of the frame. Lens sharpness also varies by fstop. Most glass is "softer" wide open and performs best stopped down a bit. Most lens manufacturers will show the Modulus Transfer Function (MTF) of their products by distance from the center and by fstop in the specifications section. So the MTF of the camera with lens shows the potential sharpness you can get, but when photographers say sharpness, they really mean perceived sharpness or accutance.
Accutance has more factors than MTF. Some of the factors happen at the time the image is captured, others in PP, and some when viewing the final image. Things like light, heat distortion, haze, fog, camera shake, focus, exposure / noise happen up front. You can improve some things in PP like increase contrast, dehaze, sharpen edges and even stabilize and deblur (Topaz sharpen AI), reduce or increase noise (yes a bit of random noise in an image can make it look sharper), but you can only decrease, not increase detail in post. When viewing, things like viewing distance, lighting on a reflective print, brightness, color space, and gamma of a monitor, resolution of the printer or monitor are all factors.
Accutance is not as simple as many photographers make it out to be. Again, camera and lens give you the potental for accutance, but you have to look at the process end to end. If most monitors are only capable of displaying around 90ppi at about 6 or 7 bits per pixel, why do I need a higher resolution camera at 12 bits / color / pixel with expensive glass?