a beginner friendly distro should have the convention to install apps be by GUI instead of TUI, and guides should be updated to reflect this

It is a lot harder (and less helpful) in a written guide to tell someone to press a button in menu such-and-such; telling someone to open the terminal and copy paste a command is easier.

In addition (though I do not know if it applies so much to gui package managers) GUI apps also have the tendency to not have a stable interface, so a blender 2 tutorial will often not be useful for someone using blender 3, because the interface will have changed and buttons that were once in one place now are somewhere else or no longer exist. CLI programs for some reason are a lot more backwards compatible in my experience.

I think GUI apps should ideally be designed to be usable without the user knowing where something is beforehand (though that is not always possible, like in complex software handling a lot of stuff a new user may not be familiar with, when they only want to achieve a certain specific goal), making mentioning how the UI works almost superfluous in those cases.