The GNOME project will be 20 years old in a couple of months. So while it might feel like "every few years", we really don't change direction all that often.
As you can imagine, those that show up to do work have a great deal of say in where the project goes.
> you probably had a good reason for writing Builder instead of working on Anjuta, and that's just the way the GNOME community seems to do things.
> This makes people, especially power users, disproportionately angry because when you rewrite something
You've sort of made my argument for not changing Anjuta over the years. We knew the amount of stuff that had to be changed would leave both the code-base and UI looking very little like Anjuta. Best to let people continue using it in the mean time.
> (I still cry a little inside any time I remember Galeon.
It lives on as Epiphany and is the primary driver of the WebKitGtk backend.
This makes people, especially power users, disproportionately angry because when you rewrite something, it will be different (that's sort of the whole point);this is compounded by the fact that at the beginning it will be feature-poor compared to the older system.
"Why did you replace X with Y? With X, I could configure it to treat mouse-button-3 as mouse-button-2, but only when my USB mouse was not attached and I wasn't holding down any modifier keys."
See also: https://xkcd.com/1172/
Before I did any serious software development, I was on that side of the table being frustrated (I still cry a little inside any time I remember Galeon. Rest in Peace, my favorite browser).
I can also neither confirm nor deny that my windows are being decorated by sawfish and that I wrote a compositor in librep so that I could get modern features while using it.