By build up what specifically are you referring to? And by what turn number? Difficulty? I could see other variables as well. How many CIVs on what size map, with star and habitable planet aboundance set to what?

Im currently 49 hours into a my present godlike ludicrous abundant everything size game, Im on turn 107 and every planet (about 12) I have culture flipped, invaded, or negotiated for has no usable tiles left, terraforming has varied. But I am playing with 99 opponents. Each has from 4-12 planets.

With less players and more colonies amongst them you would expect some to be more slowly developed.

Are you referring to defenses? Some of those I have taken have had legions. Some not. All of them have had fleets, except one minor, but they somehow had two planets in the same system. First time I seen that. And both of their planets were fully developed, I demolished nearly everything on one of them, didn't need the research nor the financial buildings.