Hi Alan,
It's great to hear other perspectives, and thanks for the post. I explain below why the copy-from-the-pros method works for me, but there are many different ways to learn.
>>> Having tried the 'licks over chords' approach I now find it results in a kind of tourists attempt to master a language rather than a deeper appreciation for the rules of grammar and syntax.
Continuing with your analogy of learning to speak a language. The best learners of a language are children. They learn it by copying and imitating phrases that they hear. There is no study of rules of grammar needed or other analysis. This gets them fluent in the most natural sense, so that they can think and dream in the language. But it is not merely rote repetition. They also understand what they are saying, and make all kinds of connections, and put together new phrases that they have never heard. All this comes from copying and imitating.
This is the same type of approach that works for me in musical soloing. I play piano and guitar, and various styles in each. On piano I'm mainly playing jazz, blues, pop and boogie. For example, I can't imagine how I would learn 'boogie' piano without mainly copying other styles and riffs. It doesn't seem "derivable" to me from analyzing scales, modes, intervals, octave displacements, tonal centers - just seems like a bag of riffs, at least that's what works for me!
I've heard many students who have put too much time into scales, modes and theory, and not enough copying-from-the-greats. IMO, the results are very unmusical. Of course it's essential that in the copy-from-the-pros method, you need to also understand the theory of why the riffs sound good, so that you can properly integrate/modify them in your playing.