i think the line between retro and contemporary for consoles is defined by internet connectivity tbh. the n64 only had internet with the n64dd (which didnt last long), whilst the ps2 and the dreamcast had internet support built in or via some adapter. so i think the line of "retro" stops at the n64/psx era but thats just me. the term will be subject to change anyways as time goes on so it doesnt really matter

I’m still surprised the DS and PSP can be emulated.

If the MiSTer can't play it, it's not retro.