It is not that bad. The tunnelling contract 1 was signed September 2012 and work completed January 2015, and tunnelling contract 2 was signed November 2013 and work completed August 2016, and stations contract was signed late 2015 and was supposed to complete in 2020 but will complete in late 2022 pushing opening to 2023. So tunnelling contracts completed in 3 years, and station contract will have taken 7 years, 1.5 years of those during a pandemic. Seven years is similar to the Spadina extention I think. All these projects seem to take 7 years.
Really I would expect most stations other than the most central stations from Cedarvale to Mount Pleasant and Kennedy to reach substantial completion this year, and that all the street holes will be filled in except for Yonge-Eglinton. Right now they are just pouring concrete like crazy. Many of the central stations didn't have a shovel in the ground until 2017. Mount Pleasant only started in 2018 focused on a storm sewer and only really getting to the station in late 2018 with them pouring half the station box roof in 2019, and the other half at the very beginning of 2020.
I assume that the reason all three contracts didn't get signed in 2012 is financial, but you can't start the stopwatch until a contract is signed.