If sheep go astray even with a shepherd, what should we expect of sheep if they have "no shepherd"? When people turn away from God and "go their own way" (Isaiah 53:6) its like what it says in Judges 21:25, "In those days there was no king in Israel; everyone did what was right in his own eyes." "No king" can be the same idea as having "no shepherd". That is, no one to set things in order and to lead people in the right way. And the outcome of doing "what was right in his own eyes" is what is made clear in Proverbs 14:12, "There is a way that seems right to a man, but its end is the way of death."
So, what do people in this world need today when they have no Shepherd: COMPASSION! Jesus was "moved with compassion" for this crowd of people moving through life without a clue as to where they were going. God calls us to be compassionate with people. Part of compassion is showing people mercy and understanding. They need to know that we will listen to their cry and we will show them the One who can turn their lives completely around. Note what Jude said in verse 22 (NKJV), "And on some have compassion, making a distinction." That last phrase in the NLT is, "...those whose faith is wavering." A lot of people try hard to have faith, but they just don't know where to place it! We can show them the Faithful God who provided a perfect Savior/Shepherd in Jesus!
There's so much more to be said. For the moment may I encourage you to avoid condemnation of unbelievers. They need to have someone who will be understanding and patient with them. They need compassion.