This is a common observation among new players, but once you realize that players are trying to survive/thrive/succeed at every level, specialization becomes a self imposed handicap the higher up you go.
Yes, players at the most basic level - professions (aka vocations) - can specialize, and the game encourages and rewards players to do that. To become really good at anything requires specialization, but you cannot function well at a kingdom level with a single specialization. Rather, you need many groups specializing in many things and so kingdoms, at least vocationally, look an awful lot alike.
Where they mainly differ though is in the biomes and tribes and people and lore as well as their physical locations on the continent. You will have very different experiences from one kingdom to the next for this reason even as a specialist in the exact same craft.
The biomes will expose you to different kinds of flora, fauna and resources.
The tribes will expose you to different social structures and architectural styles.
The locations will better lend themselves to certain kinds of playstyles than others - the extremes being more isolated and survival oriented with the centers being more metropolitan and trade oriented.
And as for the people? Well if you've played a lot of MMOs then you know that not all people are the same either. Finding a group that you like and can work well with is just as important as everything else. :)
Welcome to CoE.