But more importantly, while the "frozen at the Pleistocene" approach is false - and already known to be false, no serious scientist believes that literally nothing changed since - it is also true to large extent. The Pleistocene is a huge amount of time, and in the short amount of time following it humanity diverged quite a bit - yet, we find humans extremely similar, mentally. From aboriginal Australians to Africans to Europeans to native Americans, mentally humanity is extremely close. That is very strong support that while clearly evolution continued after the Pleistocene, major things were already set by then.
While this is undoubtably true, this is one aspect of the criticisms of EP where I can understand where they are coming from. This is due to the history of EP. I do capitalize EP to distinguish the strain of psychological thinking and research primarily flowing from a relatively small group of researchers who owe much of their intellectual heritage to researchers at UC Santa Barbara from the generic view of placing psychological findings into an evolutionary perspective.
The critics were right that EP is _basically_ rebranded sociobiology. Now sociobiology flamed out very quickly due to the backlash that EO Wilson received after the publication of his book Sociobiology in the mid 1970s. No only had adaptationist perspectives in biology not entirely taken hold, there were numerous academic disciplines almost fundamentally opposed to the idea that culture (and humanity) was not entirely arbitrary. Hell, in 1983 after Derek Freeman published his debunking of Margaret Mead's claims about the Samoan people, the American Anthropological Association passed a motion declaring his work unscientific and _irresponsible_.
This milieu where EP formed was absolutely toxic to any claims about a (universal) biological influence on behavior and held nearly to an axiom that talk of genetic variation which influences behavior was inherently racist, sexist, etc. Take the controversy over the Bell Curve, published in 1994. The entire book, save one chapter, dealt with claimed genetic factors which influence behavior that broke down by class or socioeconomic status. A lone chapter dealt with race. Yet the initial controversy and the book's legacy is that of being racist. Nevermind the fair more numerous claims about the role genetics played in arranging people into social and economic classes. The mere mention of biological variation influencing behavior was a tactical move that virtually no scientist would touch.
With this backdrop, EP was developed. Honestly, marginal scientists trudging away in the relative backwoods of academia began to synthesize a perspective on human nature that took our biological past seriously. The obvious route, and probably the most common route, focused on human universals. Anyone with a basic understanding of biology will understand the general thesis of this strain of EP. All humans everywhere dealt with a shared set of problems: (1) finding food and shelter to survive (classic selection) and (2) finding a mate so that you can pass you genes to the next generation (sexual selection). There are derivative issues which arise from our shared experience like being able to cooperate with non-kin to form basic societies or being able to detect cheaters in all realms where there is a risk of someone being a free rider.
Taking these basic claims about shared human experience, you can begin to apply them in slowly expanding circles to many facets of human behavior and psychology. But the core will always be about human universals. There will always be variation, but they are variations on universals. This is precisely why many who are unversed in the actual work of EP have the instinctual worry about EP focusing too much on the Pleistocene. The Pleistocene is a safe refuge for a perspective that develops in a hostile intellectual climate. It is also tactically a wise strategy. Focus on universals to gain credibility like say with David Buss's 1989 paper "Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures". Go broad or become smeared.
As you say, there is unlikely any researcher in EP who gives any sort of credence to the notion that our psychology was 'frozen in the Pleistocene', but especially historically, there was little place else to go. Beyond that, there are mounds of fascinating findings which only need to focus on how much our psychology has _not_ adapted that it has kept researchers busy for quite some time.
That intellectual heritage along with the fact that the gold standard in EP (legitimate cross cultural work) is extraordinarily hard and expensive combined with our infantile understanding of genetics makes doing serious work in understanding the ways that post-Pleistocene environments have shaped our psychology very, very difficult indeed.