I'm a little stunned that they didn't even bother to create a Rocketry II mastery with a "Staffed Space Flight" project for those who disabled the Science Legacy path.
Civ 1 had three positive game ending conditions: Space Colonization, World Domination, and reaching the End of Game year (2020-2100 depending on difficulty). Civ VII's sandbox option has fewer win conditions (full domination and Age End) than a 35-year old game. (And yes, I know all of Civ 1's ends were technically "scored victories" but work with me here.)
Essentially Firaxis is saying "you can play in your sandbox, but you can't win (without a massive slog) if you don't play our way." That's so amazingly passive-aggressive, vindictive, and petty that I can't help but admire it.