Nobody is sure who has said it; it's been ascribed to Paul Kanter and Jerry Ruben; Robin Williams used to use it in his act.
The implication I always got from the saying is that people who were there in the '60's so fried out on those recreational drugs that they also blasted away any memories of the '60's.
Well, I doubt it was Rubin, who ended up as something of a Yuppie and who was of the view that activism and drugs didn't really mix. Although, in June of 1970, I did personally see him smoking pot and/or hashish and drinking cheap red wine (Red Mountain Burgundy in gallon jugs being passed around) at a party in LA.
There were some people who got that fried out, including some members of some of the SF bands -- I knew at least half-a-dozen kids I went to high school with who literally fried their brains and turned themselves into almost zombies -- but for the most part, we all survived just fine, thank you. Some people get flashbacks, some people don't. YMMV is about all I can say about it.
I think the original import of the saying was intended as a put down of the (relatively numerous, actually) people who never got involved with the counterculture at all and for whom the "sixties" weren't a whole lot different than the "fifties" (which ended in 1963 with JFK's translation to Heaven by LHO).
It depended where you lived/went to college. In California, it arrived fairly early on, by 1965 at the various University of California campuses (except Riverside and Irvine), in the high schools by 1967: just in time for the teens to flock to San Francisco for the Great Summer of Love. Curiously, the real hippies were beginning to move on from SF about that time out to the countryside in many cases. A couple of guys I'd known growing up who were several years older than I was were living in SF in and around the Haight-Ashbury district and going to SF State in the early '60s, were involved the Diggers (who provided free food, clothing, etc. to young runaways, etc.) and the band/drug/party scene.
The best way I can put the change is that when I graduated from high school in 1966, only half-a-dozen or so kids in my Sonoma County high school class (and fewer in the lower classes) had tried pot (other than the "Mexican" thugs, generally referred to as "pachooks" -- from pachuco who were known to smoke "reefers"). When I returned home from Virginia after my first year in college, probably 70% of the then senior class had tried pot and probably 80% of my own classmates had tried pot, though I would put the number who smoked frequently as less than 25%. Serious recreational pharmaceuticals always remained a lot less common than people now think. Even if you went to Golden Gate Park in the Summer of 1967, I'm would suspect less than half the kids hanging around did anything more than smoke pot or maybe a litlle hash. Maybe 20% really did much LSD. Most of what was advertised to kids as mescaline or psylocibin was actually acid, often cut with amphetamines (speed).
Back East, outside of NYC and maybe Boston and Chicago, things came much later, peaking I would say some 3-5 years later than in California. Eastern and Southern colleges were very preppy still in the late 1960s, with alcohol far predominating as the drug of choice. Even musically, things seemed very different: when I brought my Airplane, Doors, Grateful Dead, Big Brother, Moby Grape, Country Joe, etc. albums to college with me, most of my fellow freshmen did not know the bands or what to make of the music -- they were still into the earlier Beatles (pre-Yellow Submarine/Revolver/Magical Mystery Tour/Sgt. Pepper), the Mamas and the Papas, etc. Or Simon and Garfunkel and Arlo Guthrie if you were from NYC....