I have trouble with Siri setting a timer, telling me the weather, or letting me turn on and off individual lights (it used to do this). Data mining might be some of it but I don't see how that is an issue with a timer.
Just yesterday, though, I said "Hey, Siri, navigate home" and that literally got into a failed state. The first time I did it it told me I didn't have a "Home" contact, so I made it. Didn't work when I was in the car yesterday, but it did just now. So, I agree, there are issues with Siri.
The biggest “WTF” moment was when I was using Siri in Russian, and told it to “lower the volume” (as I’d done hundreds of times in English). It lowered Siri’s volume, but nothing else (and told me as much).
Never did figure out how to adjust my music volume with Siri in Russian.