Been looking at St. Luke 15:1-10 today. Notice that Jesus doesn't say "those who think they are righteous" but those who are righteous and need no repentance. Surely, some would say, this doesn't mean they are righteous. And surely, some would say, we don't want to exalt those who are sinners as if sinning is a good thing.
How about we just read what Jesus says. He says there are those who are righteous and need no repentance. They are the ninety-nine who are left in the desert.
It is the repentant sheep (read "found by Jesus") over whom the angels rejoice in heaven. So, good to be a sinner with a Savior than a righteous person who needs no repentance.
This theme occurs over and over in St. Luke: Jesus did not come to call righteous people but sinners to repentance.