The phrase „if you see a painting you know there was a painter” is only valid because we have actually seen people making paintings. But no one has ever seen „God” in the process of creating the world. The fact that you can’t explain something does not make it a miracle. If someone made a time travel to ancient Greece, and saved people suffering from a deadly infection with antibiotics, the ancients would probably give thanks to Asclepius, since they would be unable to explain the „miraculous” cure, even though it is a perfectly natural process.
There is a very important thing which you Christians always tend to ignore. Even if it must be conceded that an intelligent creator exists, there is absolutely no reason to believe that it is the Christian god. It could be Zeus, or Hathor, or Quetzalcōātl, or any of the countless deities venerated by various cultures in different historical ages. Or it can be a totally unknown entity as well.