Sorry, but I strongly disagree that you can balance the game around how the single player experience plays out. The AI is so poor it totally changes the face of the game
Yes, that's a problem with AI, not a problem with the approach of trying to balance the game for single player. Yes, AI has always been a problem in video games, especially strategy games. It will likely continue to be a problem for a long time... maybe forever. Maybe even after we invent quantum computing.
But there have been a multitude of strategy games that have given an excellent single player experience for many people (just maybe not for you), so we know that it can be done, and balanced reasonably well enough, even with limitations to AI. The key is to camouflage the AI's weaknesses, not make them glaringly obvious as 1upt has.
I understand that you think the only 'true' challenge is to play other people, and in some ways you are correct. But, there is a different experience in SP that many people are looking for, and it isn't all about it being 'easier.'
There are many things that SP offers that you can't always get in MP. SP allows you to go for different types of challenges than MP allows, such as record scores/times. It also better facilitates role playing for many people who enjoy that. Not to mention the frequently horrible quality of people you encounter online, especially cocky kids. Not everyone wants to deal with random internet turds when they sit down to relax to a video game for a bit. Not everyone online is like this, but enough are that it likely deters many from even bothering to play online.
You may not find SP exciting, but some people do. I'd even venture to say that "most" 4x game players in general do. Go look at a site like civplayers.com, then look at Steam's listing for people playing Civ V. I guarantee you will find an enormous disparity. Civplayers.com isn't the only way to play online, but it's one of the larger gathering places. And in this version, due to MP failings all round, it's an absolute wasteland.
That means that SP is worth balancing, and we already know that it can be, your 'strong disagreement' aside. We know this because we've seen games that do a good enough job of it before. Dozens, if not hundreds of games. Civ V just isn't one of them. You need the right design approach. Usually, that means an approach that camouflages AI weaknesses in general, which 1upt spectacularly fails to do. In time, AI can only get better. MOO, MOO 2, Galciv, Galciv II, AI wars (even though it uses enormous handicaps), and other games... heck, even Civ IV compared to Civ I... games like these show that progress is possible, even if we aren't quite at the finish line yet.