The last thing pagans and polytheists need is to become more like standard religions. Even though a culture may have worshipped pagan gods, families had individual practices and relationships with those deities. Many of those religions also have practices like ancestor worship, blessing or enchanting farming equipment, sacrifice of animals that were done by families for individual needs. Since a few people who are polytheist or pagan believe in witnessing or spreading the faith, I doubt they'll get much bigger than they are now. And as society moves away from religion, you'll probably get things set up more like the temple in iceland that was built to the Norse gods. They're open that they are atheists, and do not believe that deity exists.They simply have set up a temple for a connection to their ancestral past. They wanted to provide an alternative for people who didn't want to get married, have funerals or celebrations for holidays in Christian churches.