but why they alwayse do Rome and Greece Better
Notsure what you mean by this

RTW has many factions with excellent rosters, some with better, more balanced rosters than either the Greeks or the Romans.

Two of my favorites (Armenia, Germania), can literally run over, around, and through anything a Roman faction can send at you. Pontus has a very good unit roster, as do the Carthaginians or the Gauls. What you might lack with a particular faction, you can often make up for by recruiting mercenaries.

The one thing the devs did slant in favor of the Romans is nearly unlimited money. That's how the AI is able to spam endless stacks of "toy soldiers" to throw at you.

As to diplomacy, it would indeed be nice to have a functional diplomatic system in place, but the TW system is slowly (very slowly) getting better. If you've been playing since the days of the original Shogun, you'll know what I'm talking about....