Let me get the easy stuff out of the way,

Naxalite Insurgency - The Naxalite problem started at a time when the Congress was in power in the state. The problems (not going into it in this discussion) started in the late 50's and the tinder that sparked the full blown fire (that is still raging now) was when the state police under the Congress fired on protestors in the village of Naxalbari in 1967. The CPI (M) did not come to power for another 10 years.

There was no one bloc of communists in WB (or in the country). In 1970, the CPI colluded with the Congress to deny power to the CPI (M). The CPI (M) once in power persecuted quite actively the cadre belonging to the CPI (ML) and this goes on to this day.

There was no active pursuit of communism with the capitalist Indian govt as there was never a capitalist Indian govt. Indian governments have been socialist at best, with Indira Gandhi taking it to a higher level of socialism. As I explained earlier, the Congress colluded with the CPI to prevent the CPI (M) from taking power. The CPI (M) actively worked with the Congress officially and the Congress cadre (unofficially) to persecute Naxals and CPI (ML) cadre.

As to their legacy, they utterly ruined West Bengal. First, let us look at their record of outright murder and thuggery.

In the state assembly, the then CM (in 1996) said that the state of Bengal aka CPI (M) had seen a total of 28,000 political murders (this is the official figure mind you, and hence the unofficial figure could be much higher, but we will only go with this) in the period when the CPI (M) was in power (at that point when the statement was made) which was from 1977-1996. That is a murder every 6 hours for 19 years.

Calcutta went from being the pre eminent entrepot into India and the commercial capital under the Raj to being the 6th in the rankings of GDP per capita today. Mumbai ofc took the top spot.

Industry utterly stagnated.

The crude facts of the last 20 years about the relative position of West Bengal industry are nothing short of stunning. In 1980-81 West Bengal produced 9.8 per cent of the industrial output produced in India. In 1997-98, which is the latest year for which we have the numbers the share was 5.1 per cent, up from a nadir of 4.7 per cent in 1995-96. Organised sector employment actually declined in West Bengal over the period 1980-97; in particular employment in the organised private sector went down from 10.84 lakhs all the way to 7.99 lakh. Source. If you go back in time, the fall is precipitous. In 1959, this figure was at 22%. From 22% in 1959 down to around 7% that it is now. WB now is 11th on the Industrial output charts Source.

While Agriculture did marginally better and services did reasonably well (though the cities of Mumbai, Gurgaon, Bangalore, Chennai, Hyderabad and Pune did exponentially better), the overall management of the economy was terrible under the CPI(M),

Under the CPI (M) WB also missed the IT and ItES outsourcing boom - West Bengal for instance accounts for only for Rs 15,000 crores (under $ 3bn) of software exports, while for comparison Tamil Nadu (90% of this from Chennai) exported Rs 1,00,000 crore (approx $ 15 Bn). Bangalore accounted for $ 45 Bn of exports and Hyderabad came in at about $ 11 Bn.

As you can see, the scale is utterly off here.

Aside from this, the CPI (M) also engineered some terrible practices to win elections. Chief amongst these being allowing illegal migrants from Bangladesh (mostly Muslim) and then giving them legal status by providing them documentation. One source on this this has caused a lot of local tensions and it even became a poll issue for the 2014 elections.

In summation, the CPI (M) in their long, murderous rule did not a lot of good for West Bengal.

Otoh, the First democratically elected communist govt in the world, the CPI in Kerala did pass some stellar land reform bills, but the central govt under Nehru dismissed them on some flimsy pretext. The govt of Nambodripad would have been an interesting one to study in contrast, but we don't have the chance to do so.