"Useless".
I use Siri all day, every day for everything ranging from operating my smart home (lights and temperature), playing music, setting reminders, adding or changing my schedule, setting timers, quick calculations, asking sports or general knowledge questions, etc etc etc.
Useless, right?
Siri understands me perfectly and is able to deliver on correct commands and find answers to my questions. It works fantastically.
For comparison, I recently added an Echo Show that was on sale and I thought would fit nicely on my bedside table. I've gotten so used to controlling my HomePod with natural language that when I added the Echo Show, its inability to understand natural language and the need to remember to say things in specific commands really threw me off. This is the most popular voice assistant?
Aside from its expandability through Skills, Alexa is nowhere close to as good as Siri where it counts. I'd put Google and Siri at about even with Google ahead on general knowledge pulled from its search engine but Alexa is way behind the pack. Siri is also expandable with Siri Shortcuts which is getting a lot of support in the year that it's been out so there goes Alexa's main advantage.
"Alexa, turn off the lights"
"Sorry, I didn't find a device named lights"
https://twitter.com/metromanto/status/1161007750543024130?s=12
This is just unacceptable in a smart home assistant.
HomePod and Siri are far better than they get credit for.