I've recently started writing a terminal emulator (because...) and it's surprising how many capabilities of even the vt10x's are not supported properly by most terminal emulators. Never mind the newer ones like the VT420 with ReGIS and Sixel support etc.

Terminals seems to have gone largely backwards in terms of capability. I guess largely because they're mostly used for the lowest common denominator, and beyond that people move to web/gui interfaces, and so little software requires a more capable terminal.