It's interesting to explore and try to replicate what the big players offer, I used open source tools to create a fully automated yet customizable talking storybook maker a year ago, that can generate much better video presentations. Check out some technical details in the following article if interested: https://rshu.medium.com/crafting-personalized-stories-with-ai-a-look-into-the-multimodal-storybook-maker-311afd0fae95