Civ5 is a lot more moddable than most other strategy games (and will allow people to mod even the core game). Sure, it would be nice to have user-friendly WYSIWYG editors for leaderheads and an easy-to-use interface for adding techs, etc. but at some point it's unrealistic to expect a developer to create tools that are way better than what they use themselves without additional compensation.
Also, and I know you will call me elitist for that but couldn't care less, I don't think I would enjoy most mods that were made with such tools too much because they would most likely just add stuff. To really change the game rules or AI, you have to code, there's no way around it. And a strategy game is about its rules and AI for me, in contrast to an RPG like Oblivion where just adding stuff is actually meaningful.