I wouldn't go that far. Most distros have switched to GNOME on Wayland by default, and Fedora 34's KDE spin has switched to Wayland too. Sway is niche but not insignificant anymore (I use Sway).
X11 is definitely not dead yet, though. FLTK programs, Wine, and some game engines still require X11.
+1 for Foot. Much faster than Alacritty (esp. with PGO), supports ligatures and colored emojis (and any charset [inc. emojis] uses font fallback at a configurable custom size so you can get emojis to fit in one cell), and also supports an optional client-server mode in which all terminals share the same processes to massively improve startup times.
It's also much faster to build than Alacritty on a low-end machine, which is appreciated.
- Decoders and encoders for video, images, and audio - graphics libraries - Many parts of fast cryptographic libraries
This is typically for performance-related reasons.