What was that in reply to?

Technical image quality ultimately comes down to the quality of the glass and the quality of the sensor (itself mostly a matter of size.) These days, an APS-C DSLR and one of the APS-C mirrorless cameras (Canon, Fuji, Sony) will all have close to identical image sensor quality and the only real difference is the glass.

Plus, Sony does make a mirrorless full frame camera (and there's the super-expensive Leica) both of which will exceed any APS-C camera, at least sensor-wise.

Practical image quality is almost always a matter of the photographer and how they take advantage of the lighting available (or added), and other than noise levels, a really good photographer with an outdated camera that seems "bad" by will usually beat an average photographer with the latest and greatest.