Well, there's a bit more to it than just that.
Much of the success of current working Wayland is due to XWayland patching.
This runs X11 and XServer as a backend - on Wayland. If Wayland is to replace Xserver, cutting out the middle man... This is clearly counterproductive.
The point, of course, is that the developers know full well that is a patch job but hope that by making Wayland the new standard, it will encourage and increase open source support for fixing Wayland to operate as intended, without an XServer.
Which is somewhat amusing since the strongest complaint about X11 is that things were patched - then left that way for years at a time. Why do they think it would be different on Wayland, given that Wayland sat gathering dust for 16 years?
With X11, patching was fine since it restored it to full working order.
But with Wayland, patching by using an XServer utterly defeats the purpose of using Wayland in the first place: To remove the Server in the middle.
Either way, this is pre-planned deprecation for the future, not an immediate dropping of support. It seems more P.R. to me, than an actual action.
"We are writing this down now, because we hope someday it will be true."
GTK is maintained by Gnome (GIMP ToolKit). Gnome in the past couple years has removed huge swaths of what GTK can do
Summary
Toolbar & Related Widgets
GtkToolbar was removed.
GtkToolButton, GtkToolItem, and GtkToolPalette were also removed.
Status & Info Widgets
GtkStatusbar was removed. There is no direct replacement; applications are expected to handle status updates differently (e.g., inline messages).
Traditional Scrollbars
GtkScrollbar was removed in favor of overlay scrollbars (GtkScrolledWindow now automatically handles scrolling).
Applications no longer control the scrollbar appearance, and scrollbars are now hidden by default unless the user interacts with them.
Tree & Icon Views
GtkTreeView and GtkIconView were deprecated.
GtkCellRenderer (used for inline editing within GtkTreeView) was removed.
Action-Based Widgets
GtkAction, GtkActionGroup, and related APIs were removed.
Text-Related Widgets
GtkTextView's features were significantly reduced.
GtkTextTagTable was removed.
Event & Input Handling Changes
GdkEvent API was removed.
GdkKeymap was removed.
Deprecated Drawing APIs
GtkStyleContext and GtkStateFlags were replaced with GtkSnapshot, a node-based rendering system.
GdkPixbuf usage was reduced.
Window Management Changes
GtkDialog lost many of its automatic behaviors.
GtkWindow no longer supports client-side decorations (CSD) by default in some configurations.
GTK 4.2+ (2021-2023)
GtkTreeModel and GtkTreeStore are discouraged.
New GtkExpression-based binding replaces GtkListStore.
No More Stock Items
Stock icons and labels (GTK_STOCK_*) were removed.
Applications must now use GtkImage with manually specified icon names.
Removal of X11-Specific Features
X11-only functions in GDK were removed in favor of a Wayland-first approach.
Custom Drawing Changes
GtkDrawingArea lost direct GDK drawing support, requiring a shift to GtkSnapshot.
in order to prepare it for Wayland, limiting the functionality it once had in order to adapt it to the speedier, but less capable Wayland.
Much of this also relates to Gnomes years long persistently stated desire to emulate Android in touch only activation and no window management.
We definitely can see a very clear trend. And this is remarkably similar to the trends we observed in Microsoft and Windows OS, whereby seizing control of the product, then limiting it, allows the maintainers greater ability to subject the End User to Forced maintainer behaviors and acceptance of maintainer wants.
Now many of us give the warnings - this repeat pattern of behavior that landed us all here in the first place from MS and Windows... and we are often greeted with "Well... I mean... I guess it works. It's fine, I guess."
Here's the problem. Load up your latest Distro that is 100% Wayland only right next to the Older system using X11. Start launching apps. Compare the two, side by side. After a short while, you will begin to notice features missing. Tools missing. Buttons that used to be there - now gone.
You do not even have to do the comparison, just stay up to date with this forum with users complaining about the changes taking away tools - Like the Screenshot ability in Gnome now having integrated the Screentool into the Shell. It's reduced.
Then again: "Well, I mean... I do not really use those tools. So I don't really care."
You are one of Millions of users and of those millions, hundreds of thousands to millions do use those tools, rely on them, need them. No one uses Every Tool. But every tool is used by someone.