As an EU citizen, you cannot overstay in EU or Schengen area and must be allowed entry.
As a Canadian citizen, you cannot be denied entry to Canada and you cannot lose your Canadian citizenship without voluntarily renouncing it (other than if you obtained Canadian citizenship by fraud or misrepresentation), even if you obtain or get another nationality recognized .
If you have a valid Polish identity card that establishes your EU (Polish) nationality, it is a valid travel document in any EEA country and Switzerland and it is a Polish document recognized by Polish border guards.
From Polish Border Guards' website, regarding dual citizens:
W związku z pojawiającymi się w ostatnim czasie wątpliwościami, co do zasad dokonywania odprawy granicznej przy przekraczaniu polskiej granicy państwowej przez obywateli RP z podwójnym obywatelstwem, uprzejmie informujemy, że wymóg okazania funkcjonariuszom Straży Granicznej podczas kontroli granicznej polskiego dokumentu paszportowego lub odpowiednio dowodu osobistego dotyczy wszystkich obywateli polskich.
With regard to recent doubts concerning the rules for border checks carried out when crossing the Polish border by citizens of the Republic of Poland who are dual citizens, we would like to inform you that the requirement to present a Polish passport or, respectively, an ID card to the Border Guard officers during border control applies to all Polish citizens. (Translated by DeepL)
It also allows you to pass the exit check of the Schengen Area or another EU country. So you can travel to Italy or France, and you can pass the exit check when you leave Italy (or another EU country) for Canada without problem.
When you enter any EU country again from anywhere, your Polish ID alone also suffices.
You will need your Canadian passport and present it to the airlines when you are travelling to Canada (and most countries which do not accept Polish ID as a valid travel document).