Except you’re not a developer working on a game that has accumulated 11 years of assets and issues, and it was simply impossible for them to do it all at once.
Therefore, they preferred to adapt the expansion as it is and mostly rework the older content afterward, and they will continue to do so later.
Why is it a problem if it’s easier for them?
People have been asking Naoki Yoshida for a graphical update for years, and for years he has been explaining that it was difficult to implement.
