Replace individual boards or remove the entire floor?

Hello!
We are renovating a house from 1913 and have significantly changed the floor plan on the ground floor.
Now I would very much like to keep and refurbish the floorboards, but there is a large hole right in the middle of the kitchen area (there used to be a bathroom there). Is it worth simply filling the hole with floorboards and refurbishing the floor, or is it better to remove everything and start anew? I wonder how noticeable it is when individual floorboards are inserted?
I would be very grateful for your experiences!

Without knowing further details, I could imagine consciously designing a specific part of the floor differently so that it ultimately looks as intended. Of course, that depends on the planned use, but a change of material (e.g., natural stone or similar) can work quite well. However, I would rather consider whether "refurbishing" alone is the right decision, because first you have to see to what extent the wood can be sensibly refurbished. Often, in older houses, simple boards were nailed down, and then the question arises whether that makes sense. In addition, there is the question of whether you want/need to insulate underneath or whether there is some "stuff" under the existing floorboards that you would no longer want there based on current knowledge.

Actually, there is already Terazzo in front. The floorboards still look quite nice at the top of the rooms, so I thought I might keep them downstairs as well. What kind of stuff would one not want to keep?

Okay. I'll take a look! I haven't found any Siberian larch in the right dimensions yet. But I'll keep looking! Yes, Molly always lies in the holes not that it's that comfortable…

What kind of stuff wouldn’t you want to keep?

They are just thoughts and we don’t know the situation. I have already opened floors and then told myself that I wouldn’t want to have that under my living room floor in the long run. Starting from nests, little animals or remains of unidentifiable material.
It’s also a question of which rooms are underneath, whether you need (sound) insulation, whether there is a risk of moisture underneath, etc.
As I said... just thoughts.

If you want to tell the story of the house, you could cover / fill the areas without floorboards with a different material. I can imagine that a simple, modern seamless floor with a well-chosen contrast color can create a very individual and great effect. Somewhat elaborate, as it does not fit the current substructure, but from my point of view very appealing.