I guess the F1 screen is really important to you, but I'm looking at VLC's F1 screen right now and it looks worthless to me. It's just some links to online materials. Could mpv have that? In principle, yes. Is it worth the development effort and technical debt? I doubt it. If you're the sort of user who balks at this, it will be the least of your worries anyway and you should almost certainly use VLC instead. I think VLC is a very good program (albeit with very poor documentation) and I recommend VLC to almost everybody who asks me for a recommendation. The reason VLC's poor documentation doesn't stop me from recommending VLC is because I think most users will never need to consult the documentation in the first place.
But, if somebody is the sort of user who might find themselves wanting to consult the VLC documentation, say because they are trying to write their own extension to VLC, recommending mpv instead is a no brainer for me. mpv doesn't give you an F1 window with a clickable URL to the manual, but anybody who's capable and inclined to write scripts to extend their video editor will not be hung up by such a minor omission. And when they do manage to land on the documentation for either editor, mpv's documentation has a much better chance of actually having the information they're looking for.
> What problems does that have? What arbitrary commands do you have?
Concrete example: I control mpv from a media library application on my desktop. I can load a playlist of files from that media library into mpv. When mpv starts playing the next file, it can send a message to the media library notifying it of this. VLC can do all of that too; so far so good. In addition to playing the playlist, from within mpv I can also select files (without playing them), tag them, or delete them. When my mpv scripts do these things, they send events to the library application over the same interface that the library application is using to control mpv. As far as I've been able to determine, there is no VLC equivalent so I would need to open another communication channel between the two (instead of doing this, I decided to drop VLC support entirely.)
> I don't hate CLI, I hate having a GUI that is more complex than a GUI for playing videos
I'm starting to think we're having a fundamental communication breakdown here, because this seems completely backwards to me. VLC is the one with a complex GUI, not mpv. mpv has a very simple GUI; too simple to a fault [from the perspective of most users, who are better served by VLC.] If your needs are solely to play a file, just drag and drop the file into mpv and it will play just fine. It only gets more unfriendly when you want to change parameters and configuration, which VLC has very complicated GUIs for while mpv does not.
> Is there a practical reason to not have F1 invoke the shortcuts
In principle it could display shortcuts in the psuedo-GUI. Displaying the shortcuts in another window or in another application would require platform-specific code to be maintained for this, and I'm guessing that none of the mpv developers think that is worth their effort.