The reason Nebula and Dropout work is they are making their own content. Since most anime are sourced from the Manga or Light Novel sources, I don’t see an independent streaming company being able to get the rights and $$ to make animated content to stream. Also, animation is both expensive and takes a long time so any independent platform would need 2-4 of funding after making content to be able to survive long enough to make season 2 of anything.