My read is that, if it can’t run on an old 486 from the early/mid 90s, then it should look and sound like a game from that era. ANSI/textmode graphics, the iconic 16-color EGA palette or the two ugly four-color CGA palettes (yes, I know there were more than white/cyan/magenta/black and green/yellow/red/black in CGA, those are the two most common ones), PC Speaker beeps, OPL-sounding background music, all those are hallmarks of DOS gaming as someone who lived through that era.
(You know, games like Wolfenstein 3D, Doom, Zone 66, Solar Winds, and One Must Fall 2097 ALSO being from the 90s and exceeding most of, if not all of, those constraints. :v)