Like many different industries, even experts can be wrong when they look at things with a committed viewpoint of paradigm, immersed in a given context. Cargo shipping businesses don't find a cost-effective use for older ships. Conceded. I am fairly aware of the problems due to my years of seasteading research and participation on top of a graduate school case study/courses on international container shipping and logistics during my first attempt at grad school while working full time.
Consider: there's a huge market in used autos (fleet vehicles) from rental car fleets and corporate fleets. These vehicles sell for a significant portion of their new price, better than the average used car price for similar models and years. Rental fleet managers don't make these decisions in a vacuum, there is good and solid evidence that it is more cost-effective to replace them early than to maintain them in the fleet service.
That doesn't mean they have no value, quite the contrary, the best value to the fleet manager comes from operating/renting NEW vehicles with customer attraction, low maintenance costs (still under warranty from the dealer/manufacturer for almost every conceivable mechanical issue), they probably don't even have to change the tires on most of these vehicles before they sell them. But lots and lots of individual families are driving lease returns and former fleet vehicles that they purchased for a reasonable price with lots of life left in them.
The robust market in used ships, with thousands of commercial vessels for sale world-wide, puts the lie to the idea that these ships have zero effective value. Otherwise, they would simply automatically scrap them rather than listing for re-sale. The residual resale price is a fraction of the original cost, it's true. The cost of maintenance goes up with age, it's true. It eventually becomes more difficult to certify them with a shipping bureau, true. Most of these things are issues primarily related to using them for cargo and passenger transport across long distances. Changing the use from trans-oceanic routes to regional loitering/itinerant "tramp steaming", de-coupling your travel plans from delivery schedules, de-coupling your business model from cargo management, changing your profit margin expectation to include permanent residence for crew and families makes a big difference in the value proposition.
It's common for people to talk about ferro-cement yachts as having less value. It's true people don't pay as much for a used ferro yacht as they do for a used traditionally-built yacht in similar condition. That doesn't mean that the people who own that ferro yacht receive less value from using it.
So once again, I'll make an attempt at educating "the auditorium" on an economic point: cost is a numeric measure, price is a signalling mechanism, and value is entirely individual to circumstance.