"the actual gaming experience of a game shouldn't factor into whether or not you should buy that game".
This is what you're saying. Mods exist. Sorry. They play a huge role in how fun the game is. Not factoring this in is stupid.
Community work should not effect purchase of a game. Say you have a damn horrible game, like DNF, but it has some good modders, do you really think that justifies buying that POS ? The devs would basicly be selling a toolkit for the price of the game. Thats just wrong. Or would you be ok if say TES VI was just tool kit, while priced at $60 ?
All that does is say its ok to make poor products, and the modding community will pick up the slack. To me, its stupid to reward people for other peoples work.