I think the biggest problem with HomeKit is that for most people the primary UI for their smart home is a connected speaker, but a $150-$300 HomePod isn't something you can scatter all over your house the same way as a $20 Echo.
The iPhone, Watch, iPad, or laptop can all do the same thing as HomePod speakers.
Which is a shame, the original one has such good sound quality for its size
I would say the HomeKit is a quiet product that has a lot more use than you might think.
Is it though ?
Using voice commands feels more like a gimmick to me. The only time I ever use it is when I demo it a visitor ("look, I can control my house using my voice") but in reality I never use it. If I want to control something manually I just use a wall-mounted button or my phone/iPad. But mostly I don't control things at all, the whole point of all this 'smart' stuff is to automate things. If I have to manually operate something, I consider that a bug and try to fix it.