I believe that 'colder and wiser' and '3:11 scrub' are exactly right. The court of public opinion here in the US has ruled that running for a high school team, then for a college team, are of paramount importance. Everyone weighing in on this thread other than those I mentioned and maybe a couple other posts confirms this. This has 2 effects. These were touched on earlier, although most of you reading this will not be jumping up and down with joy at my conclusions.....
The 'school-sanctioned system' (I'll call it that but it isn't really an official system operated by a particular organizing body; it is actually an approach or way of thinking) identifies and primarily encourages talent up to the 5k. Sprinters come out of the woodwork, and occasionally one is good. Once in a while one of them is great. This is also true of those whose genetics are ideally suited to 600-1k and (a different genetic profile yet again) 1500-2M. There is no shortage of parental, school-paid coach, and sponsor support to those crowds. Those in that last group who really do have some distance genes but less true mid-D genetics and talent, (ie Lagat, Komen, or Houlihan as opposed to Brazier or Ajee) may excell at 5k down to 1500 and will not be ignored. It depends upon where you are and the HS 'system' there, and whether or not parents allow/encourage participation even if you're not making cuts, but that could be the last (most slow-twitch) profile to be noticed as teenagers.
If your ideal specialty events are all beyond that range, the aforementioned 'system' may leave you out. That final group may include some who's best event is around 10k. One can be very good at 10-15k and still no slouch at anything longer than a mile (Rupp, Haile). They are unlikely to be aware (Rupp/Salazar probably were, but many won't be) that their body is ideally suited to something longer than 10 minutes, and possibly 30, as teenagers. However, anyone who's going under 27/31 some day can probably run a 3k ahead of the average teen, and therefore be allowed and encouraged to race such.
But what if you're a natural-born marathoner with 98% slow-twitch? What if your aerobic system is off the charts by any metrics but not your anaerobic? Some folks - Haile, KB, and Kipchoge being excellent examples - have great range. None of them was about win 800 golds, but they could all run 5k and therefore could have been HS stars, then NCAA champions, not realizing yet they could break new ground in the marathon. Most of us, however are not them. Most growing up in the US will, if not successful at mid-D or the shortest of the true distance events, will not pursue the sport.
When teenagers regularly ran road races, you still might have. You'd ignore the school-sponsored track team, but winning your age group in the local 10ks, half marathons, or whatever, could motivate you to seriously pursue running. This describes the US a few decades ago. This approach was a little more inaccessible than simply joining a team at school, but you could still run if you were lowsy at 100-3000m but good at popular road distances. If you were aware of and had a ride to such events, and found success, you might have stuck with it through your athletic prime.
Although it could and did in the past, anything close to this is not about to happen anytime soon in this country. Your pure slow-twitch, small boned, marathon genetic lottery winner will simply be 'not good at sports' and never pursue one at all unless she discovers cycling. You end up not doing a sport in high school, college, or anywhere. In East Africa, you're exactly the kid everyone thinks WILL succeed. Here, we have the 'school-sanctioned system'.....
That's one of the problems. Unidentified and unnoticed talent. At your office, your church, in a class you had, on your street, somewhere, is someone who could scare the AR if she was handed over to Canova or somebody at 15. There may not be a whole lot of them, but you may have met one once. Unlike the Lyles brothers or Shaq, who very obviously excelled at something that schools, and therefore parents, value, they never knew there was something they could have been great at and gotten rich doing. Just read the thread; see what all the running fans think: This country does not care about under 25 distance runners like it does about under 25 sprinters, mid-D runners, football players, etc. You can live somewhere (Kenya, Japan) where everyone's aware of marathoning and believes it to be a valuable profession; you can discover and pursue it on your own; or you can have no idea unless you happen to be passable at the mile as well.
The other problem is less-than-ideal training. This country has fantastic coaching from. 100-1500m. The school system actually does work. The sponsored pro groups and even the NCAA turn out actual medal contenders. Even up to 10k, the US has churned out a parade of contenders over the decades. So shouldn't we have at least one 2:04-2:05 and at least one 2:18-2:19 runner at any given time? Maybe a couple of each every generation. Well, we don't.
It has been argued that the Italian school of marathon training typified by Canova and the schedules posted on this very Board and elsewhere, were largely responsible for taking the marathon from the 2:07-2:08 range the world was stuck in for decades to a new era in which 2:04-2:06 is the new world class. This has been explained elsewhere. In fact, that sentence is ripped off from Nate Jenkins. Nobody, least of all himself, considers Nate to be in the Rupp/Shalane category, but Canova's concepts and schedules allowed a mediocre guy who didn't win the genetic lottery to put up times he couldn't have imagined. Applied to the Rift Valley, they changed everything.
We still see American marathoners doing 6X1mile. 20 1/4s. These are great workouts if proceeded by 18-22 miles of moderate (as opposed to very easy) running. Done at 10k pace as the bulk of a workout, mile repeats are 10k-specific. Quarters done hard are 5k-specific. I believe the 'school-sanctioned system' is at least partially to blame here too. Runners and coaches train the way they know. If your first marathon is after a decade plus of hard training primarily for 5k, the temptation to use similar workouts is apparently too much to overcome.
Avoiding 'The Wall' is one of the primary focal points of effective marathon training that doesn't apply even to the half. Such training requires running through the wall in training and including hard running after the 20 or even 22 mile mark in workouts. After one of Jenkins' excellent essays on Blogspot, a reader commented that he wondered if short and fast work (at the expense of marathon-specific work) was being done due to habits learned in HS and college.
10k-specific workouts with easy long runs that end at the point of glycogen depletion or sooner does not a nation of world class marathoners make. Until true high volume individual workouts (as opposed to simply high overall running volume, most of which is easy) with significant doses of marathon-pace running and even faster work late in the run becomes commonplace, we are doomed to be 3rd tier. Sure, we've had Deena, Shalane, Rupp, and the Halls, but the ease with which we can name them and the time period we need to cover to come up with a list even of that size proves that they are indeed exceptions.
If we had several hundred runners throughout the country truly training for the marathon starting at the age of 20, we'd see world class performers surfacing with some regularity as opposed to the rare exceptions that we (fortunately) get now. Some are trying it now. The schedule that Taylor and Bruce at NAZ are on now in prep for NY looks good. 10M moderate followed by 10M race pace. WU and CD get you close to marathon distance. A 26 miler with 18-24 at race pace. Slightly less specific were 15 times a mile and a long moderate run of close to 30 miles. Many groups including them do 16 at race pace. There is no guarantee that the race will be perfect, but there is a guarantee it WON'T be if you don't train for the event.
Stinson had some great ones before his recent race. A 25k alternator such as Canova prescribes with 1k on/1k float. A hard 23 or 24 mile long run closing near race pace. Now, you might point out that some of these runners are not true world class performers. Stinson's race didn't go as planned. Nevertheless, more widespread use of these specific workouts can only help, especially if the true A-list American talent was all doing it.
If specific workouts were all everyone was doing with only a small amount for leg speed/turnover to break things up, most runners would ditch their non-specific 5k work and such. Get enough doing this early in, as opposed to in the twilight of, their careers, prior to 25, and some will rise to the top that could contend on the biggest of stages. We get an occasional athlete now that can. Salazar was doing something right as he coached several great marathon performances. And that's just it: it is possible, even in this country. We have had a few marathoners competitive with the world. There are more out there...