I don't think hipster fashion can be reduced to farm aesthetic from the 1940s or any other period.
People have different reasons to rag on hipsters depending on their own politics, but the universal critique relates to the hollowness and hypocrisy of the trend. From the Marxist perspective it’s pretty clearly a shout into the void, a search for meaning in a capitalism devoid of meaning, which I sympathize with. But that’s precisely the thing about the hipster movement: it rebels by doubling down on the forces ostensibly critiqued by it.
Hipsters want authenticity. From an upper-middle-class, usually white perspective, they peer into perceived “authentic” cultures often of POC and global south. This is coupled with an increase in ✨wanderlust✨, white bougie people traveling to SE Asia or Latin America with a knapsack and a trust fund, with a plan to beg their way through their travels or work an odd job if they must. Back home in the suburbs and cities, they wear choice items that seem to embody the genuine culture of elsewhere. Obviously this is a cynical and materialistic way of obtaining authenticity. Aesthetic over substance, form over function. But that’s the logic of capitalism: culture is itself commodified. Rather than culture being the totality of one’s social existence, it can be congealed into aesthetic, into clothing and vintage record players.
Individualism is another key ethic of hipsterism. The struggle for authenticity immediately confronts a contradiction with privilege. Western individualism is essentially the reflection of privilege, because as a white wealthy person, you must believe in your own difference from the masses, your uniqueness that explains your privilege. But you cannot obtain the authenticity of common folk while refusing to drop privilege and superiority. Hence another layer of hypocrisy. Culture can not only be commodified, it can be worn and removed as necessary, as one would a hat, as the situation demands.
Again, I sympathize with the search for meaning. But meaning is to be found in real existence, not in materialistic consumption, nor in aesthetic.