Depends on the lens. Most lenses hit their stride stopping down 2-3 stops from wide open. On a 50mm F1.4 lens it is already sharp at F4 in the center, it gets a little better at the corners and edges as you stop down a little more. A 600mmF4 is usually sharpest wide open. Some actually get worse at F5.6. My Sigma 150-600 Sport is best at F7.1 - F8. And so on . . .

It doesn't matter how good your lenses are, this is a simple fact, lenses have good apertures, and diffraction, which is always there, will start to be significant at F11 on low res full frame cameras, and already impacting sharpness at F5.6 on M4/3 cameras. Smaller sensor cameras don't even have mechanical apertures smaller than F5.6 or F8, resorting to internal neutral density filters to control exposure.

The sweet spot is really helpful when you are doing focus stacking - no point in going through the effort if you aren't using the best aperture to get the best sharpness. Also, particularly on fast lenses, lens flaws like field curvature, coma, chromatic aberration and other flaws are at their worst when the lens is wide open - whether you spend $100 or $4000 for a lens.

Some lenses are exceptional - like the Nikkor 105mm F1.4 - which is oustandingly sharp at all apertures until diffraction sets in at F8. The 200mm F2 is in the same company, also extremely sharp - it should be for $7000. But even it improves a bit at F5.6 over F2.

Now you can get some excellent results using F11, F16 and in some cases F22 - with certain subject matter - like macro. The reason is that your visual perception is seeing fine details magnified - even if those fine details aren't that fine. I guess what I am trying to say is that details that you look for when viewing an image at greater distances by moving up close you can see because the macro image is magnified, without the need to move in. So the image "appears" to be super sharp when in reality it is a little soft. But the perception of sharpness is informed by the unusual amount of magnified detail that you would have to move up close to see. Not sure if my choice of words is making the point.

Ignoring the sweet spot is a bit like leaving money on the table in a business transaction. No point in getting the best lenses if you are not using the best apertures for the best image quality whenever possible - creativity with depth of field aside for a moment.