I only first ran into the OFM term the other day (somehow) and I was nicely surprised at the term 'orthodox' since in the days of early Windows File Manager and DOS Shell I'd say tree-based was seen as the conventional choice.
OFM's all originate from Norton Commander for MS-DOS from 1986. It's such a foolproof concept that it has managed to live on through the transition from CLI's to GUI's and is still as versatile as ever. Two file panels, one command line, robust keyboard shortcuts, and a metric fuckton of extra functionality baked in. Including tree views.
I decided to try out Krusader on my main laptop since its all KDE programs, I have to say its a damn nice file manager. I've never used an OFM before so I'm still not used to it but I am getting the hang of it slowly. I'll still keep a traditional file manager around (Dolphin) for its strengths.
What you have to understand is that OFM's were designed to be operated with keyboard only. Once you get all the main keyboard shortcuts into your muscle memory, only then you'll be able to harness it's power. Wanna select all text files and move them to another folder in the second panel? Numpad+, *.txt, enter, F6, Enter. Done. Best part, just about every OFM will have these standardized, so it doesn't matter if you're using Krusader, Total Commander, Midnight Commander, Far Manager or even the OG Norton Commander, you'll feel right at home.
As for the strengths of traditional file managers, I can't see any. To use Total Commander as an example of a graphical OFM:
-it has Lister, which lets you view various files. From text files, images, videos and sound files, to more esoteric ones with the help of plugins like .torrent file metadata, PDF files, or executable data.
-It has the QuickView panel activated via Ctrl+Q, which turns the target panel into a Lister window. What this essentially means is that you can browse your meme folder in thumbnail view on the source panel, and as you move your cursor, the target panel previews the full resolution file. Your file manager is now an image viewer.
-It has a plethora of built-in tools, such as the directory synchronization tool, file comparison tool, multi rename tool, FTP client, file splitter/combiner file hash creator/verifier, and of course, can be expanded via plugins to include cloud storage support, SFTP support, ADB support and much more.
-It has native archive handling where you operate on them as if they were folders. You can pack files up, unpack them, modify archives, and guess what, plugins. Do you want to handle STALKER data files as if they were archives? There's a plugin for that.
-It has an extensible file search and navigation functions. Do you want to look up all the text files in a given directory that contain a specific string? That's an option. And yes, there are plugins here as well, so you can, for example, look up all the Office files that have a specific author name, or all the media files that match a specific parameter or metadata, and so on and so forth. It also has a directory tree view with which you can just type the name of the folder you want to jump to on a specific drive and it'll instantly find it so you can skip entire directory trees in your navigation.
-You can use the same plugins for file search to set up custom columns, for example to display music file metadata, and then then set up an automatic view change whenever you enter a directory that's mostly music files. You can also set up custom searches, and then set color highlights for files and/or folders that match them. Do you want for dead shortcuts/symlinks to show up as gray? You can do that. Do you want for working shortcuts/symlinks to show up as blue? Sure thing. Suddenly you've improved your file management experience by a tenfold with one simple trick.
There is so much more something like Total Commander can do that I haven't mentioned here, but you get the idea. A good OFM becomes your Swiss Army Knife you can't live without. In case of Total Commander, it quite literally is a Swiss Army Knife. Christian Ghisler, a Swiss, has been solo developing it for over three decades now, and it is as functional, reliable and smooth as a Victorinox SAK.
So I strongly encourage you to dig through every single little feature and configuration option in Krusader, because I'm sure you'll find something that'll completely change your daily workflow for the better. I've been using Total Commander for over a decade now and I still learn something new about it that ends up becoming indispensable.