Of course all sharpening methods are flawed, since they attempt to reverse an imperfectly known, noisy system.
However, an algorithm may be flawed and still be useful. What do you see as problematic in this example: Sharpening Experiments in Gimp Unsharp and "Smart Sharpening" - #4 by heckflosse ?
In my opinion the image is clearly improved by sharpening, and I don’t see any obvious flaws.