Stop buying the marketing hype. An LED display alone is significantly more complex and engineered than any mechanical watch. Every smart watch on the planet is literally full orders of magnitude more complex than any mechanical watch.
If you said, “it’s a small, simple, cool machine” that would be completely true. But they are not more engineered than nearly every other device you possess in your home, including the nearest set of $20 bluetooth earbuds.
Yeah, I forgot to mention that the longevity of the solar models is indeterminate due to new technologies. I imagine they will get better and better, though, as solar tech is constantly improving.