org-mode has an extremely low barrier to entry. I thought it seemed monstrous and magical for a while, but the learning curve is basically strictly linear (and goes on as far as you want, because Emacs).
Smartphones aren't gonna replace org-mode any time soon either: if you do any work on a laptop or desktop, you'll want org-mode. It's the best way to manage ideas and projects.
The problem is that most people now work on multiple devices, including mobile/smartphones, and expect their org to be available at all times in all places.
Now, once we have virtual terminals and keyboards in our VR headsets...
I have several of my files in Dropbox and let it do the heavy lifting. I generally only view the file from mobile. There is a MobileOrg app but it isn't great.
Smartphones aren't gonna replace org-mode any time soon either: if you do any work on a laptop or desktop, you'll want org-mode. It's the best way to manage ideas and projects.