68040 at 33MHz
128MB RAM
4096 color, 1152x832 (or similar) display
that could do Display PostScript and had a relatively complete Unix subsystem under the covers.
The Turbo Cube (same CPU but with the 24/32 bit color NeXT display board) could do full color.
Current minimum specs to be happy on MacOS: dual core 2+ghz CPU, 8GB RAM, SSD drives
Failure or not of NeXT? Not sure.