It's difficult to tell if lost/delayed bag trends are getting worse (unless someone knows where you can get good data from), but I have also experienced baggage issues with two recent flights originating at YYZ:

2024/11/20 - Mom flew YYZ-SFO. Her gate-checked carry-on was left behind and only came on the next flight.
2025/01/01 - I flew YYZ-SFO and one of my two priority-tagged checked bags was left behind. Several other passengers on the same flight were also missing their bags (including a family going on a road trip whose car seats didn't make it!). AC delivered the bag to my front door the following day.

SFO staff were lovely but acted kind nonchalant, as if they were used to handling baggage delay queries.