It's like trying to fix a dam by sticking your finger in a crack. If twitch tried to monitor this stuff they would have an impossible task and if they achieved what you want they wouldn't have nearly as popular a service.
Instead.
1) Don't watch streams you think are dumb.
I've caught myself at times watching stuff like this with the "witty" donation comments and the streamers portraying a poorly developed "character"*... is it rubbernecking? (the way we stare at a car accident when driving by), is it the insipidness of popular culture these days? BOTH. My advice, catch yourself and don't watch.
2) Do watch streamers who are doing interesting things!
3) Evangelize for streamers you think are good. Spread the word about quality content.
4) You will likely always see this garbage. Look at the TV guide, look at the movie theatres, look at popular game releases, TONS OF GARBAGE. Twitch streams are also products of their environment (in this case the aforementioned insipid popular culture), and as such we should not expect anything but mostly GARBAGE.
tldr, ignore the junk, be the change you want to see, make your own stuff or promote good stuff
*I think that reasonably minded people who think that these "genius" characters are hilarious because "I get the joke but these others dont" are as much of a problem as anything else. Take a minute and reflect on what you wish to claim is "genius"... when in most cases it's just a recycling of a previous poorly developed 'persona' that is a dumb dumb dummy dum godaamn why am I still writing here dumb me, dumb everything. Go for a walk and help someone who needs a hand-up. f*&k outta here, twitch