There are many more types of interfaces than GUIs and text-based interfaces. Voice user interfaces (VUIs), for instance, which have become commonplace in recent years, especially with virtual assistants like Alexa or Siri.

VUI's are just text interfaces with a different input system and more error checking. They implement operations that give you convenience in exchange for versatility.

Even if the two types of interfaces share strong similarities in their most commonplace usage, they are nevertheless accessed through two distinct mediums (from which they get their names (TUI / VUI)). Text is not speech, and speech is not text, and the possibility space of what can be realistically (in a human-friendly manner) provided as input or output on each is quite different. On VUIs, for instance, you can do things like query for a song by humming it [0], which would be very difficult to provide a purely textual alternative for for use in a TUI, whereas text-based interfaces make it easier to do things like looking at large swathes of structured content or copypasting a long piece of text to use as input.

[0]: https://blog.google/products/search/hum-to-search/

Where is the line between GUI and TUI? Or TUI and CLI?

Also, where does a system like Genera fits? Was it CLI, TUI or GUI?!

GUIs can have representations of text, and text input fields though...