FWIW: Marxists weren't blind to this obvious omission. The International was what we'd call a "big tent" coalition, so contentious questions were frequently hand-waved away in this fashion. Individual Marxists -- including those as foundational as Engels -- absolutely had opinions on the subject and they were not afraid to do the 19th century equivalent of Twitter dunking on those who would fantasize over establishing stateless utopias. Quoting Engels circa 1872 (bolded emphasis is my own, italicised emphasis preserved from original translation):

While the great mass of the Social-Democratic workers hold our view that state power is nothing more than the organisation with which the ruling classes, landlords and capitalists have provided themselves in order to protect their social prerogatives, Bakunin maintains that it is the state which has created capital, that the capitalist has his capital only by favour of the state. As, therefore, the state is the chief evil, it is above all the state which must be done away with and then capitalism will go to hell of itself. We, on the contrary say: do away with capital, the appropriation of the whole means of production in the hands of the few, and the state will fall away of itself. The difference is an essential one. Without a previous social revolution the abolition of the state is nonsense; the abolition of capital is in itself the social revolution and involves a change in the whole method of production. Further, however, as for Bakunin the state is the main evil, nothing must be done which can maintain the existence of any state, whether it be a republic, a monarchy or whatever it may be. Hence therefore complete abstention from all politics. To perpetrate a political action, and especially to take part in an election, would be a betrayal of principle. The thing to do is to conduct propaganda, abuse the state, organise, and when all the workers are won over, i.e., the majority, depose the authorities, abolish the state and replace it by the organisation of the International. This great act, with which the millennium begins, is called social liquidation.

[...]

Now as, according to Bakunin, the International is not to be formed for political struggle but in order that it may at once replace the old state organisation as soon as social liquidation takes place, it follows that it must come as near as possible to the Bakunist ideal of the society of the future. In this society there will above all be no authority, for authority = state = an absolute evil. (How these people propose to run a factory, work a railway or steer a ship without having in the last resort one deciding will, without a unified direction, they do not indeed tell us.) The authority of the majority over the minority also ceases. Every individual and every community is autonomous, but as to how a society, even of only two people, is possible unless each gives up some of his autonomy, Bakunin again remains silent.