Short Answer: Yes, you need a visa to change planes in Toronto
Long Answer: If an airline passenger is refused entry at a transit point or destination, the airline is required to return the passenger to the point of departure at the airline's expense (although they may try to recover the cost from the passenger). Thus, airlines are very careful to determine what documents are required by a particular passenger's travel before allowing that passenger to board. Airlines use the IATA database Timatic to reveal what documents are required.
Putting your information into Timatic through this online portal (there are others), generates this:
National India (IN) /Transit Canada (CA)
Destination India (IN)
Passports and other documents accepted for entry must be
valid for the intended transit period.
Thus, you will require a Canadian visa and your Indian passport to transit in Toronto.