When I moved from Power Desk, when it became abandonware, I switched to Directory Opus, the most used file manager here, after Explorer. Some years on, the more I use it the less I know.-michaelkenward
Unless one is constantly doing new tasks that they've never done before that's not much of a problem. Let's face it, most of us are creatures of habit and that carries over into our file management tasks as well. I suspect most people, like I have, just set things up the way they want it when they first start using their file manager and barring any little tweaks here and there from time to time most people's configurations stay static.
But it does have a reactive support forum that does not poor scorn on dumb questions.
DOpus has a wonderful forum. It's better than Total Commander's by a long shot. TC's forums are populated by people who are dead-set on doing things the way they have always been done. This is one of the reasons I moved from TC to DOpus as TC's user base won't let the author try anything too radical or new & therefore progress is being stifled.
My guess is that they all steal from one another on the front. If one does something neat, the others will follow.
File managers have been around for a very long time. I would daresay that most of the innovation that comes in that market comes in new ways to present data rather than new ways to process data.
My only advice is to not put too much stock in first impressions. Often the screen that greets you when you first run that new file manager for the first time can be tweaked quite a bit to make it very different than what you first encounter. This is especially true of Total Commander and Directory Opus and they are both things that the more you put in towards learning their abilities the greater your reward will be.