I suppose I'd like to preface this post by apologizing for my ignorance towards golden era fighters in other posts, erroneously believing that modern fighters were more technically sound. As I've studied over the years I've come to have a greater appreciation for their craft and how much of it is missing from today's swathe of fighters. This is also inspired by instruction I've received from various coaches over the years, that in retrospect, was just plain bad.
We've had some great discussions before that have touched on this topic, but they've almost always been in the midst of some other topic.
Kicking it off, these excellent articles on Joe louis:
(also Sinister's excellent posts on sherdog, which I do not have links to but are worth tracking down on google if you have the time)
Interestingly, of the few modern fighters who do display tactics, techniques and methods that were widely present in old school fighters, commentators almost always attribute it to some supernatural ability of the fighter, never stopping to consider that something they are DOING is simply advantageous.
Two things are apparent to me now: Head positioning/weight distribution, and the loss of the jab as a weapon.
Many modern fighters lean over their front foot, sometimes even doing a little shimmy that amounts to not much at all, as if to add flair to their movement. This is particularly endemic in what Irish likes to deride as the "european" style of boxing :P. When you step back and objectively view it, the problem is almost glaringly obvious. By doing so, fighters reduce the distance between the most vulnerable part of their anatomy - the head - and the opponents weapons. Now defense has to be based on peak reflexes, which is not a good deal particularly as the fight drags on, or if the fighter isn't particularly blessed in that department.
By putting the weight over the lead foot, the fighters balance is now compromised when doing anything but standing still, making him susceptible to being knocked down in tight exchanges, regardless of his ability to take a punch. The weight distribution also means he has to shift his weight back before he can actually move, should he need to create distance rapidly. The same also applies to punching, in that the weight must be shifted back to load up on punches. As opposed to a rear hip favoring distribution, in which the fighter's power punches are effectively, always ready to fire.
And now the jab: This to me, is the most interesting aspect of Joe Louis, and indeed, many of his peers of the time. The jab is held low, but cocked almost at hip level. Relaxed, but always facing outward like a fencer's sword. The result is an always present threat. It offers no telegraph, always ready to strike. Furthermore, by holding the lead hand slightly forward, the distance the jab has to travel is reduced. Effectively the "hand speed" is doubled without any change in athleticism. I don't think the psychological impact of this position can be discounted. No matter what Joe is doing, moving forward, back, left or right, the jab is constantly threatening his opponent.
Secondly, many fighters today have fast, snappy jabs that look great, but it seems the use of the jab as a weapon in and of itself has become rare, the jab has been relegated to a tool that is used to set up other punches. Joe often seems to drive off the rear foot with the jab, almost like a fencer lunges with his sword. The result is a perceptible difference in effect. One fighter who still does this frequently today is Andre Ward, who coincidentally (or perhaps not coincidentally at all...) also shares many methods of the old school including favoring the rear hip and preferring to slip to the right in various levels as opposed to exhaustive whirling maneuvers to avoid danger. Ward is not a big puncher, but the thrusting jab he has used successfully to control fights against aggressive opponents, even men much bigger than him.
Well thats my piece. Looking forward to thoughts and analysis by other posters here!