I mentioned an example in another comment - basic manipulation of timers don’t work well - like, adding time to an existing timer. When I’m working in the kitchen this is really useful. There are also major performance issues - “working on it” and “sorry can you say that again” are probably two of it’s most common utterances. Random bus like “there’s nothing playing” and the wrong siri taking over the request from a million miles away and you just can’t even hear is extra annoying.
Google Home is pretty bad at adding time to existing timers too. Sometimes it works, and sometimes it creates a second timer with a difficult to access name.
Personally, I'm become convinced a good talking/listening clock is actually a useful thing, but Google isn't providing it, and it sounds like Apple isn't either.