There is a ton of marketing associated with mechanical watches, especially from Patek and Rolex. They make Apple's marketing look like it's done by amateurs.
IMO, for a mechanical watch to be a legacy gift to a child, it should be something that is associated with the giver. For example, if a child has fond memories dad wearing his Speedmaster, then it will probably have some meaning as it's passed on. Wearing that one watch for a long period of time is what helps give it true meaning. If it's part of a multi-watch collection, then IMO, it may not have the same meaning as it's passed on.
Smartwatches will probably not be something owned over the long term, but that doesn't take away from the value it can deliver to its user. There are some people who will always prefer mechanical/automatic watches and I think that's great. There are also people who are learning to appreciate watches through the purchase of an Apple Watch. We're all on the same horological journey. Some of us are driving Teslas (smartwatches), some of us are driving Porsches (mechanicals) and some of us are driving and appreciating both.