This is a bit of a longer post. According to the official site, the Alliance is driven by "tradition", as well as justice and duty, whilst the Horde is driven by unity, as well as freedom and hope.
https://worldofwarcraft.com/en-us/game/races
However, I do not believe that is necessarily the actual case in the lore. In fact, isn't it almost the other way around? What Alliance race, compared to their Horde counterpart, is truly traditional? Wasn't the original point of the Alliance to keep their world safe and free from an alien invasion?
Humans: Not really, they lost huge parts of their ancient land as well as most of their original seven kingdoms, at one point or another. Forced to change and adapt a lot in recent decades; they can play almost every class and are very versatile and adaptive, which is why human magi are more talented at magic than the elves; also gets along well with most races, according to Diplomacy racial, look at Anduin and his tolerance towards other peoples, even to the point of alienating some of his own friends
Dwarves: Three clans living together and working in unity and relative harmony; Dark Iron clan especially has had to change a lot, giving up a lot of their former traditions as they renounced Ragnaros and joined their estranged kin; Moira's very union with Thaurissan indicates how the two broke with all their traditions to become a genuine couple.
Night Elves: Maybe they are traditional. But they also accepted the Highborne and the worgen back into their society, into their very capital. They have joined with younger races and bowed to their authority and their wisdom, look at Tyrande with Varian for example - and have completely reshaped their once-elitist and xenophobic society since ancient times. Look at the Cenarion Circle accepting the tauren and trolls into Moonglade. Look at their tacit acceptance of demon hunters, their forgiveness for Maiev, their allowing males to join the priesthood, and females to become druids. They have changed as well, a lot.
Gnomes: Very democratic and progressive, maybe the most democratic system of all the known races. Heavily modernized society. Very forward-looking perspective and world-view
Draenei: Abandoned homeworld. Became refugees, and lost most of their ancestral traditions, renamed themselves, adopted new belief system and culture. Very high level of magic and technological innovation. Have been to dozens / hundreds of planets -- exposed themselves to entirely new and diverse cultures, and have adapted in order to properly survive.
Worgen: Lost their kingdom, and their ancient home. Spread out across three continents, mingling with other races and peoples, abandoned old isolationism completely to actively engage with the world's affairs. Becoming a worgen itself is about distinctive change and adaptation.
Pandaren: Maybe. But the fact that so many of the Tushui have left the Wandering Isle and befriend complete strangers so easily implies that they are willing to bend their traditions as well.
Void elves: Embraced radical new teachings and limitless possibilities, abandoned sun reverence completely, rejecting the Sunwell's power
Kul Tirans: Also abandoned isolationism. Have reconnected with their mainlander kin. Learned to accept and forgive Jaina Proudmoore, admitting they were wrong about her all along. Female Archmage who spent most of her life away from her homeland becoming Lord-Admiral itself seems to be setting a record; I doubt there were too many of those in history
Mechagnomes: Same thing, they've rejoined the gnomes. Accepted that they do not need to renounce flesh and mortality in order to progress. High level of technology, the fact they left Gnomeregan for Mechagon indicates they were explorers willing to expand and broaden their horizons
On the other hand, tauren, trolls, orcs are all very traditional and religious; shamanism is literally about honoring your ancestors and the customs they pass down from generation to generation (essentially preserving the past) in almost everything you do and strive for. Blood elves are Highborne descendants who are extremely proud of their ancestry and heritage. The same applies to Suramar's nightborne, who are even more haughty and refined; the two races indeed walled themselves from the rest of civilization for much longer than even Greymane ever could. Goblins seem to be just that, high-tech and materialistic admittedly, but not really changing their natures despite everything. The Forsaken, maybe. Because Sylvanas has left, and Calia is guiding them towards a different future. But most Forsaken players still seem to prefer the old order under Sylvanas and resent Calia.
So what do you think? Is the Alliance really more traditional?