Late and gay, but the problem with being an indie/solo vtuber is the market is saturated to fuck and you don't have a manager to get you interesting deals or offers.
Being part of a brand like Hololive, Vshojo, Nijisanji etc is you have a built in audience thanks to the work of your peers/senpais(older talents who have been in the game longer) - Take a look at Hololive English generation 3, Advent. They debuted july 30th (ish) and they already have between 414k subs and 566k between five talents (technically, but FuwaMoco is a twin act). They also already have monetisation, which is unusual for youtube to activate for new channels.
Being part of a brand also gets you easy access to merch with your persona tied to it, you have management sorting commissions of art and designs for things like mousepads, plushies, tea pots/mugs and so much more.
An indie has to do ALL of the groundwork for themselves. You have to market yourself, you have to interact with SoMe diligently, you have to find artists that can do art for you if you aren't an artist yourself (although loads of vtubers are)
Yes, a corporation is going to take a chunk of your earnings and different corps have different ways of doing the money thing. I know Hololive members get a flat rate payment every month, plus an unknown percentage of superchats and merch sales. Vshojo does it differently and I think they take a large chunk of merch sales but the talent keeps the superchats, I'm not 100% certain however.
Plus, indies don't have the certainty to break even - vtubing is an expensive business to get started in. The models cost money, the rigging of the models cost money, you need a powerhouse PC that can handle streaming the latest and greatest games with OBS running. If you want to do incredibly niche content like ASMR, the ASMR microphone costs a fuck tonne. One of the more popular ASMR mics is the KU100, which comes in at a whopping 8k dollarydoos. Plus indies don't have access to the 3D studios that corpos do.
Indies will never have access to the full power of a corp like Cover, who have been expanding their brand on a global scale for a while, even building stupidly expensive 3D studios that are going to be used for different kinds of streams, concerts included.
An indie will never be able to rent a stadium to have a concert like a "real" idol corp.
Yes, indies go through less yellow tape and can stream whatever they want, whenever they want, however they want and they can talk like they want to. Some vtubers prefer being indie because of that, some prefer being smaller channels and not having the Japanese idol industrial complex weighing on their shoulders. Some vtubers simply aren't idols, but that's what makes the corporate vtubers more exciting to many of those who watch vtubers. It's difficult to explain because you have to have some kind of brainrot to enjoy the idol culture, but it's like watching your favourite bands holding a concert together.