They are still popular but a lot of people in general are looking for more modern look, faster/easier opening and closing (one handed use without grabbing the blade and snapping it down old school or adding thumb studs), lighter weight, pocket clip, more secure handle shape/texture, etc.
I wouldn't buy one but I would cherish and carry one given to me as a gift. It doesn't mean the crap I get is any better, because its just about the style, preference, needs, etc. of each person.
I'm sure they are plenty good still. Not all the time, but sometimes, the Golden Age nostalgia stuff causes people to think just about everything was better "back when" when it actually wasn't. Selective and wishful thinking deal of the psyche.
I would get one and return it in a week if you are curious about it and it doesn't click for you.