The situation with Glade is not because of malicious intent, please don't assume bad faith. No GTK developers are happy that Glade has basically been deprecated in GTK4, it was a necessity due to technical reasons. Note that it's only GTK4 that it doesn't work for, Glade is still a reasonable choice for GTK3 applications.

There is a replacement for GTK4 being developed, it turns out starting from scratch for the new builder format is easier than trying to refactor everything in Glade.