Looking back over back issues of Model Boats magazines, I would say the content started to suffer from the early seventies onwards.
Model boats used to be part of Model Maker magazine, and reading through issues from the fifties and sixties was a real treat for me- these were published before I was born, so I'm not looking back through rose tinted spectacles.
Lots of lovely plans ideas and drawings with each issue. When a product was reviewed, like an electric motor, technical data was published with it allowing an informed decision.
The designs of Vic Smeed were and are still relevant today, and he come up with some lovely boats that were both simple to build, but elegant in design. They also performed well.
Another modeller from that era, Peter Holland always came up with some wild an unorthodox designs. I well remember him operating his man-sized RC robots in the foyer at the ME exhibition in the late seventies and early eighties hiding the transmitter behind his back so it looked like the robots were autonomous.
The publishers could do a lot worse than revisit a few of these earlier designs, many of whom are no longer available through the plans service.