The tech tree is now less of a tree and more a series of branches. Still split into military and civic, there are several branches to go down, all of which are locked from the start of the game, and must be unlocked through completing pre-requisite conditions. From recruiting units, or sieging settlements, and so on. This gives you some objectives throughout your campaign, and shouldn’t be ignored or it’ll seriously impact your late game. These technologies will unlock new buildings, grant public order bonuses, raise the starting capacity of units, and upgrades to later game regiments.