The only thing I miss from 1.0 that I've never really seen replicated since was how in my very first game, the galaxy was broken up into two halves, one half was all big beefy centralized, authoritarian leaning nations with defensive pacts but all refusing to federate further than that, and on the other side of the galaxy, there were four ENORMOUS democracies, and between them this giant field of tiny 1-4 star empires, each of them having been diced up by wars of liberation into vassals and proxy states, and by the mid to late game there was a constant stream of rivalries, war declarations, old empires dying, new empires being founded in wars of liberation, as the four democracies basically engaged in ethics-based proxy wars between all their little semi-vassal states.
other than never seeing anything like that ever again since, everything has been a freaking blast and the changes for the better