Shiinaecchigawarubyhoshinothefullanimat 2021 -

I need to clarify if the user is asking about an official project or a fan creation. Since they mentioned 2021, and there's no official RWBY project from that year with those characters combined with others. The official 2021 release was RWBY Volume 9: Episode 9. It's possible they're referring to a fan-made animation or mod that uses RWBY characters and animates it in a full anime style, hence "The Fullanimat".