I don't feel that all fitness trackers are bad, though some use-cases for them are generally bad (such as sleep tracking). Watches are quite good for exercise tracking, and tracking exercise has legitimate and high quality value (e.g. competitions with yourself to incentivize improvement, strain tracking to ensure you aren't overdoing it, daily targets and goals to incentivize activity). The idea of all-day tracking is probably on the net unhealthy for almost all humans though.

My comment was targeted at rings in-particular, because 1. they encourage that all-day tracking paradigm, which is probably on the net unhealthy for almost all humans, and 2. their sensors are so bad that even if all-day tracking were healthy (it isn't) they physically can't do it to any degree that is meaningful.

A lot of people seem to buy fitness trackers merely to verify they sleep poorly, and then do nothing about it.