During the lead-up to Christmas, you may have heard two polar opposite camps pushing the same message -- that Christmas is not a True Christian (TM) holiday, so it would be best if we just dumped it. Those groups are, first, the hardcore new atheist types, who think they're pulling the rug out from under the pretensions of tradition for a practice that only got going during the Victorian era; and second, the church of hardcore Christian Cosplayers for whom any deviation from authentic practice of ye olden days, like 1000 years ago or longer, is heresy.
The new atheist types offer nothing to replace our existing set of rituals, and can therefore be dismissed right away. Some fraction are just lamewads who don't want any special rituals in their lives at all, and the other fraction are those who accept some ritual component to life, but only if it's asocial or anti-social, such as camping out for Hobbit tickets or clawing your fellow man during a Black Friday looting session, respectively. Coming together to go caroling, non-ironically, would be beyond the pale.
But the Cosplay Christian objection must be taken more seriously, because they do propose specific holidays to focus on more than Christmas, whether earlier Catholic traditions like Advent or even further back like keeping the Sabbath, observing Passover, etc., as the Jews in Jesus' time would have. Whatever they include, they definitely exclude practices from the pagan or barbarian groups from the Medieval period and earlier. In particular Christmas and Easter would be out due to their pagan roots.
Still, we should keep traditions that are worth keeping. How can we distinguish those that do their job well as traditions from those that do not? One quick check is to see how well it has fared over time. By this measure, following kosher food taboos would seem to be fair game for junking, as just about every religious group has done that descends from the religion of the Jews in Jesus' time. Moving from the realm of rituals to beliefs, the vivid pictures of Heaven and Hell -- of the land of the dead in general -- are among the most memorable and widely held beliefs, even though they're derived more from Proto-Indo-European and other pre-Christian religions, such as Zoroastrianism. Their success would recommend that we keep them.
In fact, when we look at our most enduring holiday rituals, it seems like most of them have pagan rather than strictly Christian roots -- not just the overall spirit of Christmas but specific activities like caroling, the rite of spring that accompanies Easter, the harvest-time indulgence of Thanksgiving, the carnivalesque role-reversal of Halloween, the calendrical rite of the New Year, and the patriotic celebrations of the Fourth of July. Or at least as these holidays existed up through the 1980s, before becoming more atomized and drained of spectacle. But hey, lasting all that time is still pretty damn good.
Is this part of a more general pattern? Indeed it is. Here is a wonderful, brief cross-cultural review of rituals and their relationship to societal structure. (They also look at how different parts of the ritual relate to each other, apart from social context.) The authors Atkinson and Whitehouse look separately at dysphoric and euphoric rituals -- the former are painful ones like initiation rites, and the latter are more enjoyable ones like public celebrations.
Their data come from a compendium of anthropological fieldwork, so they have no idea how long the practices have been in practice. But what appears to give a ritual a better chance of being passed on through the generations is a high level of arousal -- that feeling of elation or even getting pumped up. Rushing around the mall with only thoughts of gifts for others on your mind, as well as anticipating what you'll be getting in your turn, the thunder and explosion of fireworks on the Fourth of July, getting sloshed and dancing the night away on New Year's Eve, taking on a different, more hell-raising persona on Halloween without fear of being punished for it later. It's no wonder these traditions survived as long as they did -- they're just so much fun! They lift you up out of your ordinary routine and throw you into a special experience.
What societal variables have an influence on how arousing a group's euphoric rituals are? Controlling for other factors, it was only the presence of classical religion (i.e. the major "world religions" like Islam, Christianity, Buddhism, Hinduism, etc.). And that influence was negative. As the authors discuss, these religions tend to have a more literate and doctrinal emphasis, not simply a set of energetic corporeal activities that everybody just joins in without knowing exactly -- or even remotely -- "what it's all about". World religions try to domesticate the wild frenzy of earlier religious rituals.
And yet just reciting the catechism is not enough to glue the adherents together. Look at how pitiful the track record is for the various sects of Marxism / Communism. They had their own guides written in question-and-answer format, derived from some higher authority, allowing them to be transmitted quickly and widely. Yet by not offering anything exciting to ever take part in, they failed to replace religion. Far and away the strongest repulsive force of leftist sects is their joyless treadmill of an alternative lifestyle, one damned meeting after another.
Unlike modern systems of doctrine, those spawned by the world religions could only have caught on by tolerating or even encouraging the adopters to carry on some of their traditional rituals. Today, although belief in those doctrines has been fading, the pagan rituals haven't suffered as precipitous of a decline. (Though there too people these days don't seem as interested in losing themselves in ritual -- they'd rather continue their boring, never-ending session of web-surfing.)
The power of religion to bind members of a community together and guide them in their daily lives cannot be denied. But as we grope our way forward in a de-Christianizing phase of history, we should keep our eyes open to what has served us well in the past, and try now as then to incorporate those rituals into whatever new system we converge toward. Again the non-answers of new atheists means we can ignore them when trying to figure out what to replace existing rituals with, or how to modify them. At the same time, only an idiot would dismiss the Greek and Roman heritage as mere pagan philosophy and barbarian mythology, let alone the broader Proto-Indo-European tradition.
Given how uncertain this process will be, it doesn't make sense to chart out a blueprint and start ticking off the boxes once we've exchanged this ritual for that one, or modified this one in such-and-such a way. It will involve lots of trial and error, but then it always has. Still, we should remember that traditional traditions have withstood a stronger test of time than new-fangled traditions, and that we might end up relying heavily on the barbarians for our rituals, even as we rely on the civilized for our doctrines.