Buddhism was the first of the world religions, as contrasted with the ethnic religions, the local religions into which one is born. One is born a Hindu; one is born a Jew; one chooses to profess Buddhism, Christianity, or Islam.
—Joseph Campbell, Myths of Light

Paganism is not a world religion. It has the potential to become one—or rather, to become a group of religions that act like a world religion. But it's never quite gotten there.

The ancient traditions behind Paganism were all ethnic religions, but Pagans have left that behind. Different groups favor certain past cultures as their inspiration, but no one's born into them based on their nationality. Indeed there is strong pushback (thank the gods) toward any group that restricts membership by ethnicity. This is a step forward.

At the same time, Paganism has relatively narrow appeal. Think about why people come to Paganism in the first place. There are really just three types of people attracted to it:

  1. People who strongly feel nature is the most sacred thing
  2. People who have had terrible experiences with Christianity or another major religion, yet for some reason still want to pursue religion
  3. People who have had mystical or paranormal experiences that they feel are best explained by New Age beliefs

There are exceptions and outliers, but I suppose a majority of Pagans come from (at least) one of these three groups.

That is a very small pool to draw from.

I know there are many Pagans who don't want to see Paganism become a world religion. The numbers don't matter to them: this is not a religion that converts people. I agree with that sentiment, and missionizing or proselytizing is anathema to what I love most about Pagan religions. But there are ways of reaching out and inviting new converts which don't rely on aggressive or annoying conversion tactics. Such outreach is not only moderate and ethical, it's also progressive. Because the world needs more Pagans.

Yes, I'm a non-Pagan and that is my position.

Consider the values that stand at the core of contemporary Paganism. I want to see them spread to more people and entrenched more deeply in society. The ideals of Paganism—individualism, cultural pluralism, tolerance, social justice and ecological stewardship—are badly needed, and are never so clearly, so firmly, or so unequivocally insisted upon by any other religion I've seen (nor the new atheism). If more of our senators, more of our teachers, more of our parents, more of our voters were making decisions with those values in mind we'd enrich and improve the world.

The process of becoming a world religion is distilling the essence of the teachings into something anyone can pick up. Historically the Christ took the rich cultural history of the oppressed Jews and did this; the Buddha did the same for the mighty spiritual engine of Vedic tradition. Suddenly poor Romans, who were supposed to vie with each other to get ahead, could sit side-by-side in friendship, and non-Indians, untouchable filth by the Hindu caste system, could pursue release from karma like any Brahmin. There's a benefit there.