UPnP was supposed to help with this as well before it became a security disaster. There's also stuff like https://github.com/danoctavian/bluntly/blob/master/README.md to do NAT holepunching without a central server (using DHT) but again adoption and the actual ergonomics of usage (npm, the config file, key distribution etc make it fail the "could my grandma use it" test) are not easy enough to make it easy enough for the un-devops'd masses.