Okay, so you're telling me that people who are interested in doing this content dont do it because... they cant figure out how to queue for it? Sounds like a good reason to keep people who arent fit for the content out - sorry, being a bit sarcastic here, but if you fail at queuing up because you have to open a different window, I'm worried if you can manage to even get out of an AoE. Your assumption that people dont queue up for this content because they're to dumb to find the queue-window for it, doesnt really hold up. If someone wants to do this content, they'll figure out how to. Granted, they could "advertise" the RF better, but other than that its just a different menu...

I would argue that the reason most people arent doing the more complex/difficult/recent Ex-Primals through RF is the same it always has been: Getting paired up with seven random guys isnt the best way to tackle those fights, since they require coordination, communication and knowledge of the fight. So its prefered NOT to do them in RF/DF in the first place since it will lead to a lot frustation. You're just more sucessful when you can get a full team together, so thats what most people are doing.

RF has the nice addition that you can queue up with "no bonus", making farming through RF a LOT easier because you can make sure not to get paired up with new people each time - even with being a mentor, sometimes I prefer to just get my own stuff done and a Sophia-clear takes 10 minutes, not 45. So I actually like that feature very much (and we dont have it in DF).
I dont want to give up on this just because queuing up for it is a bit more of an inconvenience for the solo-player - and again I doubt that RF is the reason for that, I believe its more the nature of the content. Bismarck and Ravana are the easier primals, no surprise people are more willing to queue up for those with DF. It was the same in ARR - the easy primals like Ruda you were able to queue up for, the more difficult ones... not so much.

And: As long as those duties in RF they wont show up in your mentor roulette, so if they stay there, why worry about that? And if they can show up in your roulette, they've been moved to DF, so... there isnt a problem? Since you can just do them at that point then. Through DF. As you want.