I've not had a problem with the plastic adjustment knob on mine, other than its fragility relative to the rest of the razor. It might be the grade of plastic used now compared to earlier decades has changed.
For better or for worse? I bought mine new 2 years ago. Or, people in today's world just like to nitpick more than they did in the 50s.
Legend says he complained about the formula change to his Godfather: Who then made the CEO an offer he couldn't refuse.