Why not let a single player try competitive questing?
Because it's impossible to play multiple characters at the same time, race against yourself or sabotage yourself. You can choose which quest path to follow when the avatar's quest conflicts with a companion.
not try to be devils advocate here but after some research they spend descent amount of time on this that could been used on the single player fan base just saying.
If you take away all of the pledges made specifically for Game Master Mode, and all of the pledges/purchases based on attention of and promotion by those interested in that, would there still be a net positive amount that could be diverted to single player?
People were hired because of the Kickstarter. If the GM mode stretch goal wasn't met, and there wasn't continued interest in the feature, the same number of people wouldn't have been hired to work on extra things for single player.
So what would constitute a "reaction"?

How about 'I hope the usability features and extra attention for modding due to GM mode result in more mods available for single player, as well'?