You're right that the word "world" is often used to represent different scales in different contexts. Some scales may be larger than our planet, and some may be smaller. The context is very important to interpret the meaning. "The world of I sects" might be a science documentary about small scale nature and the life spans of bugs. World building is a phrase often applies to fantasy/sci-fi/fiction novels or collaborative games where there is an effort to build a rich description of reality that arises from a set of initial assumptions/conditions that differ from our own reality. The scope of that may be much larger or much smaller than a single planet. The word really does have a lot of uses, and the context is really necessary to understand the meaning.
In the case of this image, for me at least, "out of this world" evokes a cliche elementary valentines or A+ style sticker on a school assignment that has a picture of a rocket ship with the phrase, "you're outta this world". If you received such a sticker in elementary school, you knew you did a good job. In that reading, the OP is cleverly telling the original meme creator that they have done a good job with the meme.