I guess we should deprecate and remove DOSBox too, right?
DOSBox exists because DOS legacy applications still exist, and will continue to exist for a very long time. The same is true of X legacy applications.
DOSBox exists because DOS legacy applications still exist, and will continue to exist for a very long time. The same is true of X legacy applications.
Soon it will get to the point where the UI toolkits that matter will have ported entirely to Wayland and remove their X11 compatibility code. When that happens, all modern apps will be Wayland-native only. That leaves legacy apps and toolkits that haven't gotten with the program. For those, a VM running an old OS with Xorg will suffice. That is the "DOSBox equivalent" here.