The Parable of the Prodigal Son is not a singular happily ever after story. It was written after two parables on the same topic: the lost sheep and the lost coin, all in Luke 15. These stories need to be read together, because they are one message presented in three ways.
The prodigal son cannot be interpretted in isolation or we will impose onto God the idea that he can only save those who come home.
In the parable of the lost sheep, Jesus picks the sheep up and carries it home without its permission and against its free will.
In the parable of the lost coins, the coins are even more brainless than the sheep and cannot do anything to impact on their being found and being rescued.
These three stories together reveal to us that Jesus is capable of saving a brainless wonder, a stupid bleeting sheep who doesn’t know it’s lost, and a man who comes home with his own agenda.
It doesn’t matter what category you fall into or how little you do to “accept” God’s salvation … He is going to save every last, lost sheep.