I have an outsider's perspective, I studied economics but mostly ended up doing economic history (I am a practical person, and preferred stats to models)...

...the point of economics is not to produce models that are 100% accurate. Yes, there is an absolute ton of witchcraft in economics and especially in macro (CGE, DGE to name two areas beloved by civil servants/central banks) but it is very far from useless (and, contrary to what the author thinks, there is a hell of a lot of testing of theories). The issue, funnily enough given the author's perspective, is often that we use economics to just support whatever we already believe.

On his actual content: unsurprisingly, he gets his history totally wrong.

First, an important point, the UK never actually adopted monetarism. We were forced to adopt DCE targets by the IMF in 1968 but everyone thought it was bullshit. Even after Thatcher crushed inflation, monetarism was only popular amongst the small group of City economics/journalists who came to the idea in the 1970s (and were thought of as crackpots by non-risk takers). The UK was thoroughly Keynesian, that is why we persisted with utterly insane policies through govts under both parties (until Thatcher).

Second, saying monetarism causes disaster confuses the cause and effect. Monetarism, whatever its theoretical faults, was correct in 1979 but was only necessary because Labour/Heath had fucked the economy beyond belief (the UK went to a three-day week because the economy literally just stopped working).

Third, the 1960/70s were not a period of economic success. Inflation hit 25%, two devaluations, one trip to the IMF, one banking crisis, and endless begging other people to lend money (and the govt got a reputation for going back on agreements). Incomes policy was, objectively, one of the most disastrous policies ever conceived. It ended up, literally, with unions running the economy in 1974. Yes, growth was high but real growth was lower and supported by population growth. I am not aware of any history which concludes any economic policy pursued in this period worked. Everything failed.

Fourth, what everyone forgets about the 1950/60s was that there was almost no trade. That is why workers were richer. Most currencies weren't convertible until the late 50s. The UK could milk Commonwealth nations dry with no competition. But the evidence here is clear: trade makes us richer. Anyone who says this isn't the case, even Trump recognises this, is an ignoramus.

Fifth, Greenspan understood there was a bubble. He gave a speech in 1998 saying there was a bubble. The issue - which is perfectly logical if you look at what happened in 1958 when the Fed did burst a bubble - is that people will say you caused the downturn if you intervene (he blames monetarism for causing the downturn but also blames the Fed for not bursting the bubble...what a genius this guy must be, spotting bubbles like he is at a car wash). This is an attempt to inject some psychology into economics, it is amazing the author doesn't see this.

It is no surprise Graeber has thrown his lot in with Corbyn. The number of crackpot acolytes around Corbyn grows every day (thankfully, he remains unpopular with voters). I would vote for Labour normally...but their current policies are just...ignorant. These ideas have been tried, they didn't work, that is why Corbyn has support amongst young people who don't read books. The logic is: build a wall, make Goldman Sachs pay for it.