Well the game relies far more on threats and state gifts then ever before.

It has up and downsides.

On the plus threats get you much further then rome or mtw2 ever did. Now if you beat back a nation, and put up a sweet deal to take some nice benefits, you just push them a little with a threat and bam you get it.

On other hand state gifts are a reliable way for a financially powerful nation to send small to large gifts to get instant friendship boosts. Even the lowest one, pricey plates, will get you a boost up in the friendship chart.

It also goes alot by govt and religion, though not always the case as I kept a relationship up with India for a long time even tho they were hindu

It takes some learning but the diplomatic system offers far more then before.