Do we have to believe that good people exists?
If we may agree that good requires the skillful, then:

AN3.69:9.1: There are these three skillful roots.
What three?
Contentment, love, and understanding.

Contentment, love, and understanding are worth cultivating for their own sake without needing to assess others. Indeed, the Buddha says quite clearly that:

MN8:12.12: ‘Others will have wrong view, but here we will have right view.’

Good people acting out of contentment, love and understanding are to be found in all faiths. Good people inspire us all.