Recently, Yovana shared Water into Wine (in these arms demo) with Jon and David writing. You only have to compare it to the version of the album that included Richie in the re-writing. I think contributions are obvious.

Without Richie I think no "Wanted" , and probably Living On A prayer, Lay Your Hands on Me and Ill Be There For You would not be the same.

With respect to the songs that Jon wrote, imagine Dry County with a duration of 4 minutes and a single standard. Imagine any guitarist in the album These Days ... I'm sure it would be a very different thing.