I don’t have the time to check on every issue you mention, but I can say as a new user (coming from Sibelius and Musescore) that my experience is far less disappointing.
From the very ground up, Dorico is different from other scorewriters. It has a different design where almost every notation is modeled as a meaningful object or property in the program. Moreover, the internal representation of many elements of the score is different from what a Sibelius/Musescore/Finale user might be used to. This makes the program less intuitive for some, more intuitive for others. It really depends.
It is reasonable to think, though, that all these choices might come at the price of a steeper learning curve, because the program has more “entities” and “properties” and “actions” to deal with compared to the competitors. Think of CAD systems or 3D editing programs. They are really not intuitive for the casual user, but in the end this is a necessary tradeoff and it pays for the professionals that use it, once they learn the concepts and the interface.
Personally, I belong to those who find this design reassuring and easy to learn, maybe because I have a bit of a technical background. I know that when something will not work the way I expect, it is going to be much less fiddling around and looking for workarounds. These are my expectations, anyway, based on my experience as a user and as a programmer, and I hope I will not be proven wrong in the long run.
About the shortcut system: I was very dubious about the shortcuts assigned to the quick-edits of notes (combinations of Alt, Shift, Ctrl, and the arrows, that you mention). But I soon realized that they are very easy to remember, because of their consistency. Alt is for “edit”, the vertical axis is for changing pitch, the horizontal axis is for changes in time. Shortcuts without Alt do not change things, but help you select. You have fast ways to move things around like no other program, and it minimizes the rewritings.
Not to mention the pleasant surprise of having the possibility in the preferences of specifying the language of your keyboard (I’m on an Italian layout) … all the shortcuts update consequently and they show correctly in the tool-tips! For me that is really intuitive and fast in getting me started using the program.
And the jump bar, that is perfect for discovering new commands or recalling actions without fiddling in the menus. I don’t know. All very pleasant to me.
Of course, the dangers of a similar approach are that when something is not part of the design it might be more complicated to find a workaround. If the issue is a common one, it will likely be addressed in a future release, if the design is robust enough.
So all in all… Dorico does not fear to expose the user to the logic around which the score is modeled, and to structure the interface around this logic. It creates and exposes concepts that are specific, like a good professional tool.
It is not perfect but it is brave, and as a user I feel empowered, and I have fun using it.