I'm pretty sure it wasn't on-device before. At least not all the time. But I have some good news for you, they added the ability to type your requests to Siri 😆
And to be fair, some certain things are definitely faster by voice than doing manually, like setting a timer and stuff. It's just daunting when the assistant misunderstands you or takes ages to respond. If they fixed all that, it could actually be useful.