Afraid you'll have to deal. RPG Maker is just made in a way that makes updates like these difficult, if you don't restart it leads to bugs and other issues cropping up, especially the longer you put it off.
Edit: I'm afraid disliking my comment won't change the fact that that's just how RPGMaker works, I have seen other developers make mention of this, plenty of RPGMaker game devs will suggest you to restart your file to get the full experience since they make balancing or mechanical changes to their games that might feel off if you don't. If you still feel you can handle it, just transfer your saves file into the new version, and it's done.