Man, what are you talking about?
First, there are many unique mods out there changing the game in a unusual way which makes me wonder how they did it. I have great respect for those modders - sometimes it seems like they were working harder than the original developers. And if you really want to get a new way to play a civ, I welcome you to check out my Petroleum mod which is introducing the dynamics of diminishing resources to Civilization:
http://forums.civfanatics.com/showthread.php?t=417580
Second, of course most of them are only "adding a civ, tweaking a few numbers"! Would you expect the opposite? That with this easy system to upload your mod with some mouseclicks you will only see giant mod packs with professional product values?
Pardon me, but you sound like someone who hasn't tried out many mods...