I think there's a difference between this product and the iPhone/iPads and Apple is hurt by being so late.
First the iPhone - it may not have been the first smartphone, but it combined features never before seen and started a revolution in cellular devices. The iPad riding on the popularity of iOS and apps gave people something, and finally jump started the tablet market, though tablets are still languishing. In both cases, Apple wasn't "late to the game" per say, they took an existing product that was under-utilized and improved it in a way that consumers found very useful.
Now with this Siri thing, Google, MS and Amazon have superior digital assistants and there's little Apple can do to provide something that they haven't done yet, in fact Apple will only catch up to them. So in my opinion, Apple is indeed late to the game, and is hurt by their inferior Siri. One can hope (or expect) to see a vastly improved Siri but until I see it, I'm not so sure
They are late, and Siri is arguably inferior to Google. It isn't inferior to Alexa. Alexa's main advantage is the microphones, so Alexa gets better input that is easier for it to correctly understand. Alexa has the Applications. But I suspect the vast majority of users are like myself and my retired Mom (who I set up Alexa for). We have never downloaded any of those features.
I think Siri improves vastly when it is connected to eight microphones. Presumably there are software improvements happening as well. That is kind of a given, really. Apple can deliver a lot of features. For example, with integration with the Apple Watch it can have different users on the same device or a different level of privacy because it will know when I'm talking (because I'm also wearing my Apple Watch and the voice and Watch are largely in the same position in the room).
I think this is will be a bigger market than the iPad and closer to the iPod (in that everyone will have this device) and the smartphone.