There are other examples too, New York, etc.
To put in perspective how lowly densified Toronto is heres some numbers.
Toronto 4149.5/sqkm
Paris 20,000/sqkm
New York 11,232/sqkm
Ottawa 317/sqkm
There are lots of benefits to densification for large cities. Less time commuting, cheaper costs of living, cheaper administrative/Infrastructure costs, etc.
Personally I would rather the solution being spreading the jobs out across the country and having more spread out living but we don’t wish to do that. Instead we choose to pack them into the city centers despite thanks to technology there is no longer a need.
I know I am living the opposite life of a 15 min city, in a low density city. That being said when I lived in larger cities I always preferred the idea of being able to get to where I need easily without a vehicle. No need to struggle with parking. No need to fight traffic. Etc.