Paul wrote many letters and expressed thankfulness for imperfect people. People don't have to be perfect for you to be grateful for them.
One sure sign that you are growing in grace is that you are showing more grace to others and becoming more thankful for people.
Some practical Christianity - Jesus served me so I will serve you. Jesus forgave me so I will forgive you. Jesus is patient with my faults, failures, and struggles, so I will be patient with yours. Jesus showed me kindness, so I will show you kindness. Pretty amazing huh?