Bern,
Most of the text you posted seem like quoted text to me. Please correct me if I’m wrong.
In case I am not wrong, please format quoted text as quoted text. And, BTW, don’t post too much in one chunk. People will not read it (me included).
Back to the topic, more or less:
I started to dive deeper into AppleScript around 2012 or so, quite some years earlier into shell scripting, but that mainly for very specific (occasional) tasks. I’m using Macs since 1994.
In my experience :
With AppleScript you can do many things, with AppleScript-ObjC you can do even more things. Never had a need for JXA. But I like it, because the JavaScript syntax is way easier than the damn AppleScript syntax (which, ironically, was planned as an “easy’ syntax with its similarities to natural languages.)
How to learn it (the “climb” as you name it):
If you are not pressed (by your chief or something), then just let it evolve: You’ll find things in your every-day life you want to automize. Then just do it. Thoroughly. I mean, that one task, thoroughly. Look up the resources on this forum or on StackExchange, etc.
By programming that one task you’ll learn more than you’ll learn with courses (IMHO).
The point is that you don’t have to “know” AppleScript. Nor any other language. However, it is good to know more of AppleScript, and of other languages. But it is also good to know just something about other languages, because this gives you the possibility to look at an object from different perspectives.
It’s a bit like with natural languages: The more languages you know (or practice) the better you understand your own language (this point is very important!) and the easier it will be to understand new ones (and to wrap around any things in general.)
Just my 3 cents
– Tom