As far as I can tell, only modern equivalent of the terminal (a generic input/output device/program that can be used as the standard front end to an endless arr

As far as I can tell, only modern equivalent of the terminal (a generic input/output device/program that can be used as the standard front end to an endless array of applications) that has gained any appreciable traction is the web browser. Any "modern terminal, but not actually a terminal" experience, using current tech, is going to be built on top of a web browser. The browser is just the terminal though (which to be fair is a large piece of the puzzle); we still don't have the shell analog. The inadequacy of ChromeOS does not make me hopeful. ChromeOS is to the browser what midnight commander is to the terminal.