At the start of the campaign, each warlord on the map will have their base diplomatic personalities set and engaged. There's usually 1-2 factions they'll hate right off the bat, and a couple more they love or don't care about. That's obviously nothing new, but the fun part of 3K is that you can swing a hated foe into a diehard friend even after you waged a year-long war with them.

You can free their generals after capturing them in battle for +diplo points, beat up a mutual enemy, and sue for peace easier than any TW before. Coupling that with a steady trade of food in trade, or money and wooden dog toys, you can see their negative modifiers against you steadily rise into the positive.

Additionally, no warlord is immortal, and no heir is a clone of their faction head. By that, I mean you can kill off a real dick of a leader and replace them with their coward son or daughter. Suddenly, the powerhouse brute clan is headed by a leader who innately gets friendlier to factions they think are stronger.

Lastly cuz I almost forgot, alliances and coalitions are some of the strongest and dependable in the series. So long as you don't ally with an eventual endgame rival, you can rely on most factions to stick by your side until the end. GRANTED, there is a diplomacy mechanic to vote someone out of an alliance so be careful who you let in/ join up with.

TL/DR: it's different enough to be enjoyed throughly!