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Of course it matters, but how much does it matter?  Half of the top programs from the first half of the last century aren't even FBS anymore. 

I get what you are saying but I think "half" is a bit of an exaggeration.  Here are the top-20 from 1900-1949:

1	Notre Dame	0.83221	359	62	26	447
2	Michigan	0.77962	319	83	20	422
3	Army	0.75390	323	95	31	449
4	Minnesota	0.73961	291	95	23	409
5	Alabama	0.73864	312	102	26	440
6	Yale	0.72184	300	107	28	435
7	Southern Cal	0.71691	277	100	31	408
8	Dartmouth	0.71016	294	112	27	433
9	Texas	0.70961	314	122	22	458
10	Pennsylvania	0.70851	328	127	27	482
11	Vanderbilt	0.70740	302	117	27	446
12	Tennessee	0.70114	292	115	33	440
13	Harvard	0.69839	291	118	27	436
14	Ohio State	0.69419	282	115	33	430
15	Princeton	0.69048	260	108	31	399
16	California	0.68812	266	114	24	404
17	Pittsburgh	0.68467	305	134	24	463
18	Utah	0.67439	236	108	23	367
19	Nebraska	0.67396	279	128	27	434
20	Cornell	0.67290	279	131	18	428

Off the top of my head, the no longer FBS are:

• #6 Yale
• #8 Dartmouth
• #10 Penn
• #13 Harvard
• #15 Princeton
• #20 Cornell

So that is 3 of the top-10 (30%), five of the top-15 (33%), and six of the top-20 (30%).  

I think the top of the 70- year list and Penn State perhaps not getting its due is that it's the only team in the top 12 that didn't play anyone else up there.
UNL-OU
UF-UGA
UF-FSU
UM-OSU
AL-AU
USC-ND
OU-UT
UGA-AU
.
Everyone else had a strong rival to parry & joust with.  Penn State..........won that "Best in the East" trophy every year.  They had to beat out.....who?  Syracuse?  Big whoop.  
.
Maybe that's why they may fall short in many people's eyes.

It doesn't stand, it was just the Ivy League voluntarily demoting their athletic departments in order to devote all of their resources to academics. 

They started sucking because they stopped awarding athletic scholarships. 

It's not the same situation at all as Minnesota, Nebraska and Tennessee falling off of a cliff without any kind of status demotion conference wise; teams that are still trying to be good but can't. 

Fordham might be a better example, but their success predated your specified time frame. 

Because a "helmet" defined by us is a different list than one made by a 20 year old.

Because a "helmet" defined by us is a different list than one made by a 20 year old.

I'll give an example.  I remember back in the late 1990's sometime I think it was Nebraska was very highly ranked and they were about to play Oklahoma.  

Oklahoma had a great run that ended with three consecutive 11-1 seasons from 1985-1987.  They lost to Miami, FL in each of those seasons (Orange Bowl in 1987, road in 1986, home in 1985 and finished ranked #1, #3 behind PSU and Miami, FL, and #3 behind Miami, FL and FSU.  Oklahoma had been consistently elite from shortly after WWII up through 1987.  From 1948-1987 they were:

• #1 in win% by a LARGE margin over #2 PSU.  
• #1 in AP Appearances over #2 tOSU
• #1 in AP top-10 appearances over #2 tOSU

The point is that they were REALLY good from 1948-1987.  Then they pretty much sucked from 1988-1999.  Their best seasons in those 11 years were 9-3 campaigns in 1988, 1991, and 1993 and they were:

• #41 in win %
• #20 in AP Appearances
• #18 in AP top-10's

As the Oklahoma/Nebraska game in (I think) 1997 was approaching I was desperately hoping for a Nebraska loss because the Cornhuskers were ranked ahead of Ohio State and a Nebraska loss was one of the things on my mental list of everything that needed to happen for tOSU to win the NC.  

I was talking with my dad and he said something to the effect of "Well Oklahoma is pretty good."  This statement made absolutely no sense to me.  I only had a vague recollection of the very end of Oklahoma's great run up through 1987.  Most of my CFB fandom coincided with the 1988-1997 and Oklahoma had been generally terrible.  They finished .500 in 1994 and 1995 then went 3-8 in 1996 and they were below .500 in 1997 as well.  Additionally, they hadn't beaten Nebraska since 1990 and this was when they still played every year so six consecutive losses from 1991-1996.  Worse, the recent losses hadn't even been close.  Oklahoma lost to Nebraska 37-0 in 1995 and 73-21 in 1996.  From my youthful perspective, Nebraska was a major National Power and Oklahoma was chopped liver.  My dad, being much older, remembered Oklahoma's great run.  To him, as a casual fan, Oklahoma was a major national power even though they hadn't actually been a major national power in about a decade.  

That right there is "Helmet".  

Oklahoma's greatness was great enough and long enough that casual fans like my dad still thought of them as a great team even when they weren't.  

Now consider a school like Clemson.  They've been phenomenal under Dabo Swinney.  They haven't finished with more than two losses since 2011 and they've been Alabama's main competitor in the CFP era.  They've won 2 CFPNC's and played in five CFPNCG's.  Their pinnacle is very high but their success hasn't lasted very long.  I mentioned that they haven't finished with more than two losses since 2011 but from 2001-2011 they never finished with less than four.  Their current great run is 10 years.  Oklahoma's post WWII great run was 40.  If Clemson now enters a decade like what Oklahoma had from 1988-1997 will fans in 2030 still think of them as a great team (like my dad thought of Oklahoma) or will we think of them as an "ok team that had that one great run back, when was it?"  

So helmet status is fueled by casual fans' ignorance of current events?