Hmm, see, none of us is "most users".
On the one hand, I can see how Andrew's suggestions make sense for some people and some workflows.
On the other hand, personally I would be horrified if I had to use a Toolbox that works the way Andrew is suggesting. I have all seven selection tools lined up, ready for use, along with almost all of the other tools that can be put in the toolbox, and that works really well. And I find the LibreOffice UI to be one of the worst UIs I've ever had to deal with.
People who like things the way they are usually don't feel motivated to speak up and say so.
I like the GIMP Toolbox just the way it is.
I like being able to move the Toolbox around and resize it at will.
I like having all the tools and my preferred dialogs in the Toolbox, and I like being able to pull a dialog out to stand on its own when I want to.
I like working in Full Screen mode, with the ability to pull the Toolbox up only when needed, otherwise having it hidden behind the image.
In my opinion, the people who put together the current GIMP UI did a totally outstanding job.
No matter how much I like the current UI, and no matter how much Andrew doesn't like it, neither of us can speak for "most users". That would require a very carefully done survey, which likely would reveal that there's no such thing as "most GIMP users". But perhaps there are "exemplar" types of users and workflows, with different UI preferences.