There's more than a little truth to that one. Merchant Navy wages have historically been not that much better than Royal Navy wages and nothing like what other merchant marine's pay. Perhaps that explains the large number of British officers on "foreign flag" vessels.
I'm afraid that very few container ships carry passengers. The port time is so limited that they are undesirable to passengers wishing to see a bit shoreside. My first ship, as a deck cadet, was the SS President Madison and when drawn up, as a second generation container ship, was intended to carry passengers. The plan was abandoned and, as a result, she had a whole deck in her house with nothing in it-not even bulkheads. Kind of like a racket-ball court with a low overhead! A full day in port is a long time for a container ship, and 6-8 hours is often the norm in the more modern ports. You almost have to hope for a dock strike to get any real time ashore. It's changed the nature of going to sea radically, and not for the better. On the freighters it was not uncommon to spend a week in port. "Break-bulk" freighters are the thing to look for in that department. The ones I sailed in carried 12 passengers, the max by law without carrying a doctor, and you are correct in that they were a wonderful way to travel. You knew the itinerary somewhat, but it was subject to change due to the dictates of cargo. Usually that meant additional ports and a longer voyage all at no further cost to the passenger. The last one I was on was in the late seventies and she made a 90 day voyage between the west coast of the US as far as Pakistan, hitting pretty much every decent port in between! (with the exception of Australia, but then you've seen that) This was available for the princely sum of $3500 US and I vividly recall doing the math on that one. You couldn't live the same three months ashore for the same money. Nothing fancy, but with your own room, library, saloon, and dining with the officers. The food, as on virtually all ships, was excellent.
Those ships were more labor intensive and carried a crew of 45-ships today are down to 19 commonly. Needless to say the position of baker, and all the morning delites he delivered, has been eliminated.
There used to be a publication called Freighter News and it was the guide to such ships. There was always a waiting list for passengers.
The trouble with the passengers is that they were all too old to take full advantage of the experience. If you're only going to be in Singapore for two days sleep is optional! Even if it's without sleep, two days is an awfully short time to fall in love and still get your heart broken at leaving. Somehow we made the sacrifice. I always thought that the way to do it would be to get a group of friends who's company you did not tire easily of and just take off at a young age-sort of the way some kids travel around Yurrup after college before settling down to career and family. The oldsters just couldn't do it all and amazingly, without fail, made it back to the ship for every meal! Can you imagine being in Hong Kong and running back to the ship for lunch consisting of hamburgers?
I suspect that the majority of freighters still left are either British flag with "that' cuisine or Greek. The way containerization has gone, I suspect they are specializing in heavy lift cargo and probably do not hit as many ports as previously. if you're the type who likes to read and can entertain yourself with a book and conversation, it's a great way to travel.