Yes, but they did show that they made blessed little progress towards utopia. And two out of those three were Christians, by the way. The other, Ghandi, was familiar with Christ's teachings. He didn't get that stuff he is known for from Hinduism. He Hinduized Christian teachings. And, though unrelated to this, he failed. India and Pakistan are two separate countries who still hate each other. They both went so far as to acquire nuclear weapons to wipe the other country off the map.
Dr. King, he made progress. But he did not eliminate racism. He made some inroads to doing so, but it's still there. And people tend to forget that he wanted to heal wounds in the church. He wanted black Christians and white Christians to come together as equals at the table of brotherhood - which is holy communion. Did he want blacks and whites outside the church to get along too? Yes, but he really wanted Christians to come together as Christ intended. That's a Christian goal, not a humanist goal (though, as history shows, humanity benefits when Christian goals are reached by Christians who are focused on God rather than this world).
Mother Theresa, looking through the cold, collectivist lens which quite a bit of humanists use, you can honestly ask what good she did for humanity working in a house for the dying. Christians know the answer, we know that is a time of great spiritual need. And what she started did expand itself in ways that saved a great many lives, but she was focused on the next life, not this one. She was not trying to create utopia, she was trying to bring the love of God to those who had no reason to see it.
