Firstly, joining a corpo requires a lot of commitment in terms of time and energy. Networking. Meetings. Team-building exercises. Creating your debut presentation and possibly learning and organizing a cover. A lot of that energy is just going to be wasted. An indie could be using that same energy to put out more streams, attempt to organize merch or promotional deals, practice singing or get lessons, whatever. Stuff that would actually be useful for them.
Secondly, you don't want to sue a corporation you work or have worked for except in the most dire of circumstances. It's going to harm your chances of future employment, both as a normal person but especially as a vtuber. Oh, and lawsuits are emotionally exhausting and financially draining, regardless of how righteous your cause is. That may not be fair, but it is what it is.
I'd stay far, far away from this burning trash heap and not take any risk of getting burnt myself or risking any sort of brand damage being attached to this. If three other talents have walked away from this, they no doubt had good reason to. I'd be following their example and not go anywhere near this if I was offered anything by them.