The Pictory voiceover library offers a total of 60 AI voices from Amazon Polly and Google WaveNet, both of which offer good synthetic voices in multiple English accents. While the AI voices can't match the quality and naturalness of a human voice, they are quite advanced and are reasonably conversational so they still serve the purpose and can offer a realistic narration which is what most users are interested in.
Despite this limitation, there is a significant number of YouTube channels that successfully monetize their content using AI voices like these. YouTube prioritizes quality content regardless of its production method. Ultimately, the decision to monetize a channel lies with YouTube, but utilizing AI voices should not hinder your chances as long as your content delivers value to the audience.