I also got this feeling. I like that mechanism & I would like to see it in civ 6. It keeps you on your toes the whole game: In fact, the endgame becomes a kind of all out war, instead of the snoozefest of civ 6. & if you are careful, you can throw the AIs some techs & play peaceful. (They demand that you "cut them in for a share").
I entirely agree. That's one thing I like about Alpha Centauri. The mid-to- endgame often does become an all-out war, and usually around the time when you have a lot of new weapons and abilities to try out, which makes it even more fun.
True, it's possible but I never managed to keep the peace an entire game. At some point the AI starts making such heavy demands (all my energy, Fusion Power, etc) that I just can't accept anymore. They suddenly launch a surprise attack or team up with my neighbor. In the early-to-midgame the aggressive factions like Miriam, Yang, Santiago or H'Minee/Marr can be real nightmares (and in case of H'Minee/Marr, it can even mean a game over) But if some of the more peaceful factions survived then the games transitions mid-game into them becoming powerhouses (Usually Deirdre/Zakharov or Lal) and they suddenly become a big threat as they turn on me. (Especially Deirdre/Lal. Pacifist? UN Peacekeeper? Yeah, right)
Even after all those years I'm still in love with the diplomacy system. It feels so alive, so engaging. It just oozes personality. There are still times I actually feel hurt when someone I thought was a close friend backstabs me, cancels a Pact or starts threatening me. Or when I'm going out of my way to save a Pact Brother from annihilation from another faction. (Like Marr having launched 5 Planet Busters already against Lal who I'm allies with) In the past 20 turns I've spend all my credits and built up a massive invasion force to try and take out Marr's Planet Buster producing core cities in a last-ditch attempt to save Lal. And I'm not even sure I can succeed. Marr already has over 70 conventional missiles, and is still producing more) It's a feeling of desperation I sometimes really miss in the recent Civ games. He's also keeps trying to establish seabases close to my core cities, I keep taking them out because I know I'll be his next target)
But like I said, this game still surprises me. In another game Zakharov did something I never saw before. We were Pact Brothers, but he was easily 10 techs ahead. I wanted to pay for a tech, but then he proceeds to gift me all of his techs. (As part of my grand planetary vision, I'll grant you all of my technology. Guard this knowledge carefully, and do not forget my generosity) Even though I know it's an AI, I actually felt indebted to him.