What does "an attempt to make actual progress" mean for an evangelical Christian?

Fix any of Earth's problems aside from converting people before it's too late. If Jesus is coming next Tuesday with a new heaven and new earth, why bother fixing climate change on this one?

Why would they be a "lukewarm" christian?

If you could be using the time to save even one person from infinite torture, this is the only possible moral action, so obviously you wouldn't be truly dedicated to your faith if you did anything else