Probably OS related, I am on Win 10. Clicking on the .skp file opens it in the 2023 version. How long has it been since you have done a clean install of the OS?
Windows 11 does this feature in a better way. Having typed .skp for the file type, it then showed I had SketchUp 2019, with the new icon, for the default app. My list of other apps included three other SketchUp 2019s. As it happen, the one of the four that was chosen was 2023, so I chose the 2019 with the old icon. Double clicking a .skp then opened 2019.
Going back to the list I tried others in the list of 2019s, then noticed something: