Born in Ireland moved to Canada, now holds dual citizenship. Am I medically covered when travelling back home to Ireland to visit family?
No you are not.
Access to healthcare is based on residency, not citizenship. If you are not resident in Ireland (and not resident in a country with reciprocal agreements, such as the EU, Switzerland and Australia) then you are not entitled to free healthcare. There are some exceptions to this, but none of them appear to apply to you according to the information you have given.
Details on this Government of Ireland web page.