Either that, or a dead end. X11 stayed afloat thanks to the endless extensions, in particular Xcomposite. Windows and OSX have had full modern graphics stacks for 20-25 years, by default. OSX in particular has provided backwards compatibility in a similar fashion as XWayland does (via Carbon).

Every developer who cared about X11 has moved on; it receives little to no maintenance. We already have hardware/software where X11 is entirely unsupported. It's likely we'll see more in the future.