Wow, that's crazy.
I just booked a trip that stops in YYZ on outbound and return. The stops are about hour and half each time, hoping I won't run into issues like this. It's towards the end of the summer so maybe travel will ease up by then.
Just finished this trip.
Wasn't nearly as bad as the OP's story. The outbound was a 1:40 layover which was reduced to an hour thanks to delayed aircraft. Ran through passport control/customs got to the gate just as they were boarding. Of course the bags didn't make it, was able to see that right away thanks to AirTags. Landed in YYC and went straight to baggage office to file a claim. The bags were delivered to Canmore (about 1:15 hr from YYC) early the next morning. Still had to do some shopping though, will need to fight with AC/Amex/Travel Insurance for the refund on what we bought.
On the return, the scheduled layover was 1:13 but was reduced to 45 minutes as we departed late. From when we stepped off the plane, we had 30 minutes to clear US passport/customs and security before they closed the doors. As we were running through the airport, I got an email that we were put on the next morning's flight. I think they did this proactively because they didn't think we'd make the connection. At passport control my Global Entry wasn't working. I recently got a new passport and this was my first time using Global Entry since I got it. I went to the Global Entry line even though I didn't have the slip. The agent claimed I hadn't updated my account with the new passport number which is why it didn't work. I know I did, so not sure why it didn't work. Anyway, we finally clear everything and make it to the gate 3 minutes before they close the doors. However, there's no gate agent anywhere to be found and they hadn't started boarding yet. I went to the help desk to have them put us back on the original flight. The agent was having a very difficult time with this. I was able to check, and they were still selling seats for the flight so I knew it shouldn't have been any issues with that part. After 20 minutes and the agent making multiple phone calls, she was able to get us back on the original flight.
We left about a half hour late, which worked to my benefit. Arrived in DTW and we went straight to the baggage office to file a claim for the delayed bags. Only issue is, AC doesn't have a baggage office in DTW. I asked around and was told I'll need to go to ticketing desk for help with the bags. It was late at night and nobody was there. We let the airport and called the baggage delay helpline to file a claim. The rep was very clearly stationed overseas and was not understanding what I was needing to do. Disconnected the call and decided I'll just go back the next morning to DTW airport and file a claim at the ticketing counter.
Get to the airport the next morning and there's nobody at the ticketing counter. The flight was canceled and the agents are only present if there's a flight around that time. I asked around the airport and was told which company AC has a contract with for manning the ticketing counter. I found a supervisor from that company, who told me they can't help me but the agents will be there shortly as there's a flight that leaves in 4.5 hours. After sticking around the ticketing counter I gave up and resented to having to call the baggage helpline again. This time I got a better agent and was finally able to get a claim filed.
Long story short, it wasn't really the fault of YYZ exclusively as the connection times were very short. I wish AC would've been better about the bags delay on the return though.