Yes it is now optional
https://www.canada.ca/en/public-health/news/2022/09/government-of-canada-to-remove-covid-19-border-and-travel-measures-effective-october-1.html
As of October 1, 2022, travellers who entered Canada in the 14 days prior to October 1, 2022, will not be required to complete the remainder of their quarantine or isolation, or complete their testing requirements.
While travellers will no longer have to submit their quarantine and vaccination information through ArriveCAN, they can continue to use the optional Advance Declaration feature in ArriveCAN (free as a mobile app or on the Canada Border Services Agency (CBSA) website) to save time at the airport by submitting their customs and immigration declaration in advance of arrival.
This feature is currently available to travellers arriving at Toronto Pearson, Vancouver, or Montréal-Trudeau international airports and will expand to the Calgary, Edmonton, Winnipeg, Billy Bishop Toronto City, Ottawa, Québec City, and Halifax international airports in the coming months.