It's interesting how small the terminal was when in opened, I'm not sure when the A concourse opened (though it was mothballed for years), and the GTAA expanded the C pier in the early 00s to make it wider and added a bunch of gates on the east side (I'm not sure if this expansion was originally in the T3 plans or if it's something the GTAA came up with to deal with rising demand). In the 90s there really
weren't a lot of long haul flights to YYZ compared to how many we get today, some days of the week T3 would see a single digit number of widebodies. It really shows how things like efficient twinjets and ETOPS totally changed the economics of air travel.
And T3 was so amazingly clean and modern when it was new compared to the existing T1 and T2 owned by Transport Canada (especially T2 which felt like a bus station). I do appreciate how the expansions and renovations the GTAA has done are mostly coherent with the original early 90s architecture and design language, including how they kept the subtle use of the old Canadi>n teal corporate colours.