I would argue that spot meters are actually pretty lousy meters for general purposes. To make them shine, you need to practice precise placement of tones. They are very, very, very far from idiot proof. When you just point them at what you want to meter for, meter, and set your camera from them directly, you will get terrible exposures, due to the fact that it is a reflected meter; it tells you how to make whatever you point it out middle grey. (Incident meters, on the other hand, tell you how to make middle grey into middle grey every time. They are not fully idiot proof, but they are darned close.) With a spot meter, you have to make a deliberate decision about how to tonally render a specific part of the picture with every shot.
Of course, if placement on tones is how you want to work, they are an unmatched special-purpose tool.
Sunny 16 is not an idiot-proof magic bullet, nor do I think it is often presented as such. (Nor does it mean that you must use f/16 if it is sunny. If you want to use f/8, then do it, and speed up your shutter twice.) It is just a starting point. If the conditions are not truly bright and clear, then you need to open up some. If you go into the shade, you open up 4 to 5 stops. I don't think anybody ever said that it was simple or idiot proof. In the hands of someone who doesn't know how to judge light for its intensity and quality, it's a disaster, of course. Give any rule to someone who takes it 100% literally and absolutely, and results will be bad.
Take sunny 16 for what it is (i.e. a starting point for one's own analysis, not a fundamentalist view of the Gospel of Saint Eastman), do your own testing, and you are fine. Just like any starting point. It is better than nothing, and I would argue that it is better than an in-camera reflected meter most of the time. But like anything, experience is the real tool that matters.
Though not as widely used of a term, I prefer to say "basic daylight exposure (BDE)," as it does not get into people's minds that they must use a certain f stop.