For that matter, I would be very surprised if a non-functioning Apple Watch could be repaired easily 50 years from now.

Mechanical watches are easily "debuggable" and repairable since they are very... physical in nature. A set of small hand tools and a good magnifier usually suffice; and even parts no longer available can be relatively easily fabricated --- maybe even more easily with future technologies.

While true in general, let me present a counterpoint to that.

With mechanical watches, it is not easy at all. Maybe if you take a simple hand wind large pocket watch (fewer parts, larger parts are easier to work with, higher tolerances), then yes, but this is the "easy mode". As in electronics, equivalent of maybe Atari 2600, which you can fix with huge transformer-type soldering gun and 30-ish USD multimeters and 60-ish USD oscilloscopes. But try taking this approach to miniaturized SoC in a phone or even a smartwatch... In watches, take an automatic watch (with weight and gears which winds it up during wearing), date, maybe chronograph, moonphase, power reserve indicator, ... It will come apart to dozens of parts, some of which require special handling (hairspring), you need to lubricate all the required points, each with designated oils (maybe three different oils per watch!). Doable, but you need good knowledge, skills and expensive and maintained set of tools (e.g. look up Bergeon prices). You will also want a vibrograph and regulate the watch in different positions. If you create even a 0,1 % deviation, you are 1.5 minute off in 24 hours, 43 minutes in a month.

Yes, mechanical watch will keep for 50, even 100 years, but you are expected to have it serviced every 5 years or so and the service means disassembling it into parts and putting them back together (starting at maybe 150 USD even for 70 USD automatic watch). If you don't do that, they may work for 20 and more years, but it is hit or miss, they will wear out more and eventually when something seizes up or breaks, it will require much greater overhaul, replacing (more) parts.

An Apple Watch may be difficult to repair now because it is so miniature and modern and it is simply cheaper to throw it away and replace it with new one (this is the same with quartz calibers and mechanical watches with still-in-manufacture calibers priced less than the cost of full service).

But in 50 years, this may well flip around. As for mechanical watches, the watchmaking is somehow in demise. In our (EU) country, 20-30 years ago, a watchmaker in every larger city could service mechanical watches. Now they only change straps and batteries, maybe change entire caliber and many "modern" watch service shops (stalls in shopping malls) only change batteries. ADs (authorized dealers) all work with a single person in the entire country or even send their watches abroad. How many skilled watchmakers will be there in 50 years (two generations)? In how many countries? What will be the prices?

As for smartwatches, in 50 years we may have 3D printers spitting out entire watch-sized circuits, cheap hobbyist home-grade SMT robots, miniature FPGA capable of running entire current systems... Much like you can now repair or rebuild game consoles from 70s, 80s or 90s using cheap tools, easily available parts, 3D print a new case, or even make them into a handheld with no problems (e.g. see Ben Heckendorn's projects).

Or they could end up unused in dresser while they use the latest smartwatch.

In the end, I guess it comes down to how acceptable a real watch is as compared to a smartwatch in your social setting.

For instance, I wouldn't be caught dead with a smartwatch when visiting customers (mostly real estate companies who I write software for) the same way I wouldn't be caught wearing a mankini.

I also would not be caught without a timepiece, simply because it appears unprofessional.

I do think the kind (or lack of)of watch a person wears says something about them, much like the kind of clothing does - and I share that kind of sentiment with a lot of people.