I do like people saying this has failed/is failing when we have absolutely zero idea what the break-even point is per voyage/long run, or the operating expenses.
Currently, we know their revenue on a full cruise, and how colossal that figure is if applied throughout the year.
We also know it has very little supply, and that the main restrictor to demand is undoubtedly the price.
There's a price point that would fill up every single cruise throughout the year (and I argue it's still a pretty penny), and if its within their profitability, there's not a chance they would close this.
Also, I wouldn't be surprised if they transition to longer, cheaper per-day cruises, or variances in length of stay/stories.
New cruise ships often get put on the 3-4 day itineraries as they're cash cows. Most ships can operate at around 50% capacity and still turn a profit, and on those early cash-cow cruises, with inflated prices due to a ship's novelty, they're printing money. They could've tried to capture that with the short cruises and novel experience, and will eventually transition to more standard pricing.
Or it could actually be a failure, but hard to know outside of pure speculation.