It kind of has, although I would argue that Siri is more successful than Cortana.

If I recall correctly, the thing that made Cortana particularly frustrating and worthless is that it did all searches using Bing, and opened any websites using Edge, regardless of your default settings. You got forced to use all the Microsoft version of every tool, even if you didn't want to.

It has. Literally nobody outside of tech bloggers like Siri AI or want Siri AI. I'm pretty positive on AI in general and having used Siri AI now since iOS 27 I can say it's fucking useless and I'm about to delete it from my devices to free up the storage.

the honest answer is Apple users are historically more gullible. For example, Apple's failure with AI is twisted as a genius move by some, they are quick to forget that Apple had a keynote about the coined term Apple Intelligence and it was a big letdown. So the investment was there but it didn't work.

Siri is still subpar despite leveraging third party AI. What a genius move.

Siri is highly useful for setting timers and is a solid 9/10 at doing so reliably.

I get the impression that it is, at least to some degree

It should be fairly obvious.