Imagine you're a street performer on a really long street full of millions (7 million, to be exact) of other street performers.
At the start of the street, where the pedestrians come in, are the best spots occupied by the top performers who've been doing it for years. Most folks stop there, watch, and then leave. Then, like some great filter, folks trickle down the street. Most never go further down than the next hot act. Sure, you'll occasionally get the random outlier who comes at the street from the quiet side, but they're the exception.
This is what it's like relying on Twitch for discoverability. It's more or less hopeless. The only viable options for boosting your audience are to work outside of the street.