The problem is confusing Mission Planner with Ardupilot. You can’t really make 800 parameters easier. The complexity of Ardupilot is due to the fact that it can be used for almost any vehicle on land, sea or air. It is general purpose. To that end there is nothing you could do to improve Mission Planner except hide or turn off most of the features.
The original DJI Naza is easier to setup and use. It ends there. It is easier because you can’t do with it what you can do with Ardupilot.
There is no getting around putting in the time to learn Ardupilot if you want the return on investment.
I disagree that there is a “huge” market. DIY is getting diluted by the huge volume of RTF buyers who have no interest in building anything. It all started with nothing but DIY but as time goes on the percent of builders to appliance operators gets smaller and smaller.
Ardupilot will always be for advanced users, experimenters, professionals.