EU ROME,didn t sell well because it was...shitty.60% of the map was empty,and you had to colonise it,very few event,very many ahistorical things,altough the mods improved the game,it still was outdated in comprasion with EU III for ex(at that time) wich made EU ROME feel uncomplete
And antique era game would indeed be hard to make,with the current mechanics,I believe that s why they don t want to make a sequell.
But it has so much potential...the birth of civilisations(Babylon,Assyrian Empire),the greek wars,rome,the migrations,the fall of rome...so much potential