That’s just, well, bizarre....

Unfortunatly I think you will need to bite the bullet and replace all the kichen floor unless the originalis under that island and tou won’t know that until you remove the island IMO the whole kitchen needs aredo so maybe just live with it until you are in a position to do the whole kitchen

Yikes! I can't blame you for wanting to fix that. Your wood floors are beautiful, but if you can't easily install wood flush with the surrounding wood, have you thought of a tile floor? Then a slight variation in height may not look so strange, and you can use transition pieces between the tile and wood. Also, ask the contractor (or several) their ideas to rectify the problem.

There isn't wood flooring under the island, I can see some type of particle board through a vent :/ We also aren't planning on replacing the lower cabinets along the walls, so there isn't going to be a much better time to deal with the floor. And I just don't think tile or any other nonmatching floor will look good here with the way the kitchen is open to the other rooms and be worth the cost. but maybe I am wrong! thank you guys for the input!!

here is a picture under the island

I had exactly the same problem.

I do not know how it is done for you, but we have two layers of subfloor and, when we will renovate the kitchen in a couple years, we will fix the subfloor and put either wood or tile that will be flush with the rest of the floor..

We have a transition between the two levels, so it was not as weird as it look on your picture. Sorry for the mess, but it was just after we moved in. May be you can do something like that.

Your kitchen definitely looks better than ours! but I do think a transitional trim piece would help.
The contractor said he thought it would cost up to 15k to integrate it into the original floor! and we live in a pretty affordable area that usually has low renovation costs