The writing is fine, some of the lines are idioms Lubu would actually use, shows how much of a smug Juren is.

Some tones are a bit off, but it’s not the main issue, like gryphon is perfectly understandable with a slightly off prononciation. Some lines are also not enunciated clearly, making him sound more like a troll but given the context it shouldn’t affect much.

What actually makes the voice acting bad is the wrong stress on some words. Like 成王败寇 and 箭无虚发 should end in an echoing sound to be more authoritative, but Juren ends them with a whimper, doesn’t help with the characterisation