It is really incredible that someone can believe that from 1800 to today nothing as been learned in what regards sailing boats , stability and particularly dynamic stability.
It is also hard to believe that someone that is obviously not a professional in sail design can believe that the best professional in that area, that design blue-water boats, don't know what they are doing and are designing today worst bluewater boats than what they were doing 30 years ago, not to mention 200 years ago
One of the most trusted bluewater boats are the Halberg-Rassy. Back in 1982 they did not use a full keel anymore and their 42ft had 3.78m beam.
Today its new boat, the smaller 415 has 4.11m of beam and use a modern bulbed fin keel.
And this is not an isolated case but the norm in what refers to modern bluewater cruising boats. Sure, you can find narrower boats still made today but almost in all cases are old designs that are still produced today and that don't reflect the state of the Art neither the actual knowledge in hydrodynamics and boat design.
Happily there are very few like you, I mean that believe that know more than the best boat designers on the market, otherwise bluewater brands like Najad, Malo, HR, Moody or Oyster would still be making the same type of boats they have made 30 or 40 years ago