people tend to overrate people that were experts when oneself was in the stage of getting better. Also, when people quit they sometimes get the legend status where sometimes stories run wild, which is why suddenly some people who were slightly better than the other good experts suddenly get raised to some godlike status (krass, goldeneye... enigma apparently...). I was 14 in 2003 when I started playing EE and some others who are here now are same age as me. It's really easy to misjudge when u're that young. Example: I had plenty of "heroes" when I grew up in mod dm, with the likes of surfer, falkonetti, swarm, superfly, energ(lil later). If they had quit then I would still think of swarm being this overly amazing player and tho he really is very good I've put him "down on earth" and seen his weaknesses in many ways that I never thought he had in the past. Same goes for the others, even energy. Surfer, I can even laugh about now that I thought he was so good.
Given this, We can assume that Krass if skill is normally distributed, and that Krass is perhaps approximately 3 sd to the right of the mean skill level (z_krass ~ 3), then approximately 0.135% of people will be of equal or better skill than Krass. The game had a MUCH larger population in the past, therefore, there isn't really any reason you should doubt my claim, nor is this really all that unlikely given the larger past population of EE.
So this applies to GR too? Bigger pop -> has more experts than the lobby. (same distribution as the lobby)
My opinion is the more u play EE the more experience you get and u can use that to win more games despite your skill level being constant throughout your career. Likewise with people's IQ/smartness through history. People were just as smart in 1700 as today, but we are building upon other's achievements and learning from each other. Even a stupid person today knows things about the world the brightest minds had no clue about in year 1000. That does not mean we are smarter today tho.
Much like a child growing up, will have the same talent/IQ pretty much thoughout it's life but it takes time to learn everything and it isn't untill like 30+ u reach the pinnacle.
I believe EE has evolved, strats has been invented that people had no idea about in 2002 and thus making a mediocre player today capable of beating an expert of the past - playing some of the new strategies invented that are pretty normal to today's players. That doesn't mean that player is better tho cause soon the oldtime expert will catch up with the new ways and use his superior skill level to eventually become better.
In conclusion the players of the past were good in their time, but a game of past prime vs present prime Im sure the present would win in most setts at least. But imo that does not mean the people of today are better, they're simply just part of the higher state of evolution in the game.
But obviously, the more u have played the better u can get just like my "child analogy". So even tho the highly skilled players of the past had great talent they hadn't fully fulfilled their talent to it's pinnacle. Lets say they're still teenagers, whereas some of us who have stuck here for years are now in our 30-40'ies of the EE life
I really hope u could follow my line of thoughts there.
. As taxas said, the rest of the old players simply didnt play active enough to hold the level of skill and thatswhy the overall rating became ambiguous. A "good" player distinguish to what a good player was back in times. 
. And I also remember them not just sitting around.