Word is a word processor.
It is a tool for people who write words. That is its prime purpose.
People write words for people to read the words. That is the prime purpose.
It is a tool for readers and writers.
I am both.
I can read a menu, and scan through submenus, about 10-20x faster than I can page through buttons on a tabbed bar. The replacement is dramatically inferior in legibility and so in efficiency.
That is 1 way it is worse.
A menu bar takes a single line of text. It works perfectly in a text-only display. A ribbon bar takes many lines of small intricate graphics. It is dramatically and measurably and demonstrably inferior in its use of screen space, its use of pixels, its adaptability to other displays, its functionality for those with restricted vision or restricted computer display abilities.
This is a 2nd way it is worse.
It is not re-orientable; I can't move it to one side to use a widescreen more efficiently. Because of its poor and fixed layout I can see less of my document, meaning it hinders the primary purpose of the tool.
This is a 3rd way it is worse.
It does not interoperate with other UI paradigms. Right now I am typing on an old Mac with macOS. Word is the only Office app on it. The oldest 64-bit version of Word I can find. It has to duplicate the entire UI both in the Mac's mandatory global menu bar and in the clumsy bolted-on Windows-centric ribbon. This demonstrates the inefficiency and poor design.
This is a 4th way it's worse, although for me, it means I can ignore the ribbon and use the menus.
I read fast. I cannot squint at tiny icons and try to guess their functions quickly. It's slow. The ribbon defeats muscle memory and defeats fast reading.
This is a 5th way it's worse.
The ribbon is context-sensitive. I can't just remember what is where under where relative to the first menu, because it changes depending on where the cursor is, what is selected, what tab I left it on last time. In a menu tree, if it's left open, I tap ESC once and I am at a known place and can start over. Not with the ribbon.
This is a 6th way it's worse.
I speedread and I have good colour vision. Some people can't see colours. Some can't see fine details. Some can't see at all. A screenreader can just read all of a menu, but it can't describe icons and it can't say "then there's a vertical line and in the next section, it starts..."
The ribbon fails at accessibility.
This is a 7th way it's worse.
Menus can be accessed and manipulated in a consistent way with keyboard controls. Up/down/left/right/enter. 5 keys and you have total control. You can use this with a mouth control if you have no use of any limbs. This is good for people with motor disabilities but it is also good for keyboard-centric users with no disabilities. This is good design: it's adaptable and it's flexible and it fits different needs. But also, you can use letters to leap faster through the menu bar, so power users and touch-typists can navigate faster. All blind people who can type are touch typists; they have no other option. So this feature that aids accessibility also aids power users.
None of this applies to the state-sensitive context-sensitive ribbon. That is an 8th way it's worse.
You are wrong, and what's more, you are wrong on multiple levels, some of which I have itemised. I could get to 10, I suspect, but I have a job to do and this is not it.
Stop defending bad design. Learn to look deeper at good design that lasted decades and learn to ask why things you don't like so much survive and are widespread and have not been replaced by novelties you like.