If this is still the current default mapping, a whole lot of subtle things actually.
Things that would otherwise be better mapped. E.g.: Silend running without a modifier. Makes it too easy to accidentally drop all shilds when you're in a tight situation. Cycling through fire groups on the stick's base. That's something you might not want to require taking a hand of either stick or throttle.
Tons of functions are not even mapped. Cycling through the target's sub systems. Move the next/previous hostile to the same as general "next and previous" targeting, but with a modifier button. Frees two directions for sub systems. Where's the wing member selection? Wing nav lock? Chaff? Heat sinks? Next system in your route? Flight assist toggle (Edit: I remember that being mapped to the "mouse wheel" click on the throttle, so that might not be the current default config)?
Fair enough, yeah those are some subtle things. I have added a couple of additions to the stick mappings and am using a keyboard in tandem. I hadn't thought of some of those things you mentioned in hindsight. I have an X52-pro though, which is slightly different but it does look similar to that image.
But the standard mappings are a good base to build from. Its definitely not difficult to use, providing you tweak the setup slightly. The main axis are fine, the main buttons and other things like using the UI are intuitive and its actually a joy to use compared to learning with a pad.
I found it really easy to learn with and that's as someone new to HOTAS as I borrowed this kit specifically for Elite. I was initially overwhelmed but it all felt intuitive and its been wonderful to augment my Elite experience with a new control method. The default mappings certainly didn't hinder me, I just tweaked as I went along.
Kard, what is it specifically you're struggling with? Just be aware of some of those things Burny mentioned and you should be OK.