You have no idea what market EN indies have to appeal to, and it might not be your fault entirely. Holorot is a real issue and its pervasive throughout the community, thinking that "if we just copy everything Cover does it'll work the same way!"
It doesn't work like that. YouTube is a fucking horrible platform for livestreaming, and the only reason eastern corporations and eastern vtubers use it is because it has the largest market share in their markets of any platform with streaming abilities. That is it, its because the money is there for them. The platform is total fucking ass though. Chat delay can be anywhere between 5 to 40 seconds, making instantaneous interaction impossible. The site does not track your live viewer count properly, and probably never will again. Connection issues on the streamer side plague the YouTube servers. (speaking from experience, my time on YouTube was wrought with connection drops, while once I switched I rarely run into those issues anymore) The promotion and ability to get noticed is also nearly nonexistent. Unless you get lucky and get picked up by the algo (lmao) you are wallowing in obscurity forever. Thats exactly what was happening to Koopa, her growth had stagnated, she could not break 70 viewers a stream for months, the subs were slowing down to a crawl, (This is the experience 90% of the other indies I know and myself also experienced) and on top of all of this the copyright system of YouTube constantly threatens you with demonetization at every turn. On Twitch they at least only mute parts of your VOD if they find copyright music, which is annoying but better than having your partner status ripped away if some bot sees 6 seconds of Africa by ToTo in your recording.
Only two sets of indies can be successful on YouTube: Those who get incredibly lucky and have a miraculous boost from outside the content (Clip goes viral, gets a bunch of outside promotion ETC) or they are pandering HARD to JP Asian markets and also get lucky in finding an audience that actually gives a fuck about that. JPs and other Asian markets do not really give a fuck about gaijins in all reality and see them as more of a curiosity, a gimmick, and you cant build a dedicated fanbase on that, its too shaky and unstable. You also cannot downplay the importance of raids as introductions to networking. Raids between Bat and Koopa were as far as we know the start of them interacting with one another, and now they are on a Twitch Team cross-promoting each other. Other missive vtubers (Massive for the EN market) like Mocca, Leaflit, Lily and Shimada have exposed their fanbases to Koopa thanks to raids. None of that would have been possible in the same way without the features Twitch provides.
Also, you don't actually know how Twitch works with the content it allows clearly. She can still talk about guns if she wants to, hell she and Leaflit had an entire conversation about guns when she raided her a few months ago while Leaflet was playing a VR shooting range game.