Sorry, I meant X. Wrote X11 out of habit. But X11 is a version of X, so I still think the relevant date is 1984 and in 1996 I was still writing modelines in my X conf file... and at least with Wayland you don't have to worry about a misconfiguration frying your monitor.
As another comment notes this is more due to EDID and multisync monitors: hardware and protocol improvements in consumer electronics.
X was actually okay in 1996 on the proprietary Unixes with their proprietary graphics card and proprietary monitors. (At least on HPUX, Solaris, and Irix). Linux and the *BSDs had some catching up to do primarily in hardware support and autoconfiguration. But they did so quite rapidly.