Great middle-grade show Theodosia is a great middle-grade show that is entertaining for adults as well.
Other reviewers have mentioned their dislike of the time-period inconsistencies with costumes and language; my stance is that the target audience isn't going to care about the period costumes and won't fully understand the languages. The series moreso used the time period as a storytelling mechanism, similar to how Enola Holmes, A Series of Unfortunate Events, and The Mysterious Benedict Society are told.
Each character is very unique and has a distinct personality and set of skills. This show does a great job of showing how each of those characteristics can be a weakness in some situations and the greatest of strengths in others - a lesson the target age group needs to learn.
Is this show predictable? Yes. Is it a fantastic way to get younger generations interested in Egyptian mythology and history? Absolutely.