I agree that's a kludgy, ugly installation! What's the black box on the left of the square box? If you don't need that, you should be able to replace the square box with an octagonal one which is smaller than the chandelier's bezel. I suggest you take down the lights and see what you have there. Take a picture and post it here. Even in 1902, electrical boxes were used to mount ceiling lights (I have some in my 1895 house!).

That ceiling medallion, if pressed metal, may be an antique.

Newer versions are often of man made materials.

If you need to hide a hole in the ceiling or the cover over a hole in the ceiling rather than remove it and/or the box not recessed into the ceiling, this might give you some idea for covering it:

https://www.kinook.biz/howto-build-dropped-ceiling-light-box 

Gonna guess that black box is the thing that receives the remote turn-on signal. All of that stuff should have been put behind the medallion. Perhaps it didn't fit.

Wow you need a good electrician and no matter what what that medallion will need to be taken down and then reinstalled after the wiring is dealt with .

If your house doesn’t have light switches it sounds like you are still operating on original wiring. It is time to budget for replacing the wiring. My guess (based on one photo) is that you have a plater medallion. If so it is part of the ceiling so you will need to cut open the ceiling next to it and feed the wiring down the hole. Not a fun project but will make the house look better, function better, and be safer.