The question is - why do we still need the terminal abstraction at all?
I agree, a REPL isn't Unixy in the streams of text kind of way... or is it?
It's a bit more abstract and useful than "character-selectable" when viewed at the byte-level abstraction.
The ability to chain together utilities with no complicated data structures is extremely flexible. One of my favorite current use-cases is using FFmpeg to process RTSP streams that send output (e.g. high quality stream for recording, low quality low FPS for processing, max quality low FPS for stills, etc) to separate file descriptors. FFmpeg doesn't care whats on the other end (e.g. redirect to file, read via Python, etc) due to these lovely abstractions.
Reliability translates directly to scriptability. Yes, you can create monsters, but through the use of sub-shells and pipes I think it's the fastest, cheapest, most concise way to pull off some really cool multiprocessing tricks.
Because nobody is willing to put in the work to create a GUI toolkit that doesn't suck ass.
It's not that people want the "terminal abstraction". What people want is "Put <thing> on screen without me needing a PhD in graphics programming." That's why the dominant desktop interface paradigms have become TUIs and a Browser-In-A-Trenchcoat.
Compiz 3d effects were ultimately a useless gimmick and I predict this is too.
It's the ability to convey more information in less space.
Top-of-my-head notion: The cursor spins (or changes in another way) to reflect CPU use, or bandwidth use, instead of taking up space elsewhere on the screen.
It’s a solution in search of a problem. OP should have presented it with a real use case or benefit, not just flashy graphics, if it’s meant to be anything other than a fun oddity (which, to be fair, is perfectly fine).
So were iPods.