full range single speaker

IME, "full range single speaker"(s) are better in theory than in practice.

Full range that does it all is tough.

Some very versatile and good sounding speakers use very wide range drivers though.

A high degree of time coherency up to about 5-7Khz or so, where the majority of recorded music occurs, is their unique trait.

OHM Walsh, Triangle, Zu, and Reference 3a are some examples that come to mind.

Larryi,
Your summary of the current direction and sound of many 'modern' speakers is very astute.Why that route was chosen is puzzling and misguided.
Regards,

look here: www.iconicspkrs.com

or greatplainsaudio.com

In many cases, poor or lifeless sound is as much a result of less than optimal amplification to drive a particular speaker design than anything else.

Many modern speakers with good extended low end are also fairly inefficient and/or require lots of current to drive properly. The needed amps can become big, heavy and expensive both to buy and run. Class D amplifier technology negates much of this. Or some may chose to go with speakers that are more efficient and also likely also more (lower power) tube amp friendly.