I don't have a big, deep takeaway from my time playing this game. I like terraforming planets. I don't like getting attacked for no reason. Endless Space has much more of the former than the latter. Therefor I enjoy it.
Having played it so close to some other great 4X games, I can see some flaws I never really noticed before - the diplomacy is an unfun slog of the computer conspiring against you, your power as a faction is more or less linearly correlated with the number of systems you control, the AI doesn't really understand the combat system.
However, even with those flaws, it's a great time waster. I get a jolt of pleasure from pressing the buttons to turn numbers into other numbers, attempting to prioritize the order in which I pursue all the possible objectives even while I'm cognizant of the fact that in the long run I'm going to want them all.
In other words, Endless Space was a nice break from more stressful and challenging games. I didn't actually need it because I've had a pretty good run of fun ones for the last couple of months, but I did learn a valuable lesson - I'll want to try and spread out my 4X games in the future, so as to have these palate-cleansers available right up until the end.