Hey Maka,
I actually tried to not read any other comments until after writing my own, so I would only give my first impression, but Gwen made a very good point. I suppose I was thinking that the aesthetic was more what you were hoping to convey, since in the GDD you mentioned that it didn't fit the perspective you wanted. If that's the case, then I think it would be helpful to an artist to convey the a stylistic stand point (immediately I would think character requirements would include being rounder/squishier, more muted palettes, quirky/cartoony physical proportions, with my very limited art knowledge). You could have also shown some examples of things in the correct perspective, but my hunch would be that you'd find an artist who could translate that stylistic guide into what you wanted (ideally).
I will stand by my adoration for your Twitch integration idea. Learning that it was something that you had to sit and think about more thoroughly makes me feel like that was the whole point of this exercise, and you understood the assignment. It's both a good thing, especially in a multiplayer/party game and a good way to stretch your design muscles.
I think you did a good job under the constraints, so I wouldn't worry too much about what you didn't get finished in time. When I mentioned the genre, I did mean the listed genre in section 2.3 Genre. You have a lot of possibilities listed with question marks, which created some uncertainty for me. One reason a lot of elevator pitches reference other games is to help others immediately understand how a game is going to work, the same would have been true for this section: if you reference well known genres as the building blocks for your game, people will have an image in their head about what sorts of mechanics might be in the game. The most successful examples in this section would be "Tower Defense Battle Royale" and "TD-survival-like" which immediately gave me ideas of what to expect in the gameplay section.
About the first person thing...it's very nitpicky, but most of the doc is written in third person, "The player creates paths..." but in the audio section it switches to first person, "I don't know" or "I'd like to find." I can't disclaim it enough, it probably doesn't matter, but it caught my brain like a sock on a floorboard nail.