Most high-quality loudspeakers are 4-Ohms

It is true that high quality speakers are more likely to be lower impedance than they were 40 years ago because single driver systems, Lowther, Tannoy etc are no longer dominant. Multi driver speakers are more likely to be lower in impedance. But impedance alone is not indicative of quality high or low.

Nope. But you knew that, didn't you :)?

Stan said it well.

Count all the two ways, or book shelfs and the figures get more in line to higher impedances.

To my ears, most high-quality loudspeakers are lower impedance loads.

If you are only used to listening to systems driven by big, high current SS amps, you might that it is true. Many good, multi-driver speakers that mate well with SS amps have low impedences. However, there are many very, very good speakers with high impedences. They tend to mate well w tube amps. See for example, Vandersteen, Merlin, Coincident, Silverline, Classic Audio Reproductions, Dali Megaline, Horning, Audionote.