Utterly useless.

Can’t message people, the primary communication system for the target audience, without using cumbersome voice to text.

Can’t browse the internet, the primary use case for a modern phone.

Can’t really answer phone calls without a separate headset.

Can tell time, which is good for a watch. Has a battery life measured in hours, which is laughable for any modern watch.

Anything the Apple Watch can do is better served by the phone that you need to pair with the watch anyway, or a seperate mechanical or digital watch. Or just the phone. It takes 3 seconds to pull out a phone and look at the time.

And if you want heart rate monitoring or pulse oxygen readings: Fitbit did it first years before the Apple Watch. All Apple did was let you struggle to read text messages on a tiny screen that also tells you that your heart rate is elevated.