There are a lot of possible answers to this question, most of which would probably argue that Marx's materialist analysis of society was always inherently flawed. That said, some writers have examined the issue without abandoning Marx.

Note: I'm not a Marxist, and this is certainly not my view. It is, however, an interesting and historically important one, and I thought that since you framed your question in a Marxist manner you might appreciate a Marxist attempt to answer it.

The most famous example is probably the German-American philosopher Herbert Marcuse. After World War II, the sustained economic growth and apparent peace of post-war Western Europe and North America led him to reexamine the potential for revolution in the West. Marcuse was heavily influenced by Marxism, but believed that Marx failed to predict the ability of advanced industrial society to adapt and pacify the proletariat.

the subject which is alienated is swallowed up by its alienated existence. There is only one dimension, and it is everywhere and in all forms ...the ‘false consciousness’ of their rationality becomes the true consciousness ...it is a good way of life – much better than before – and as a good way of life, it militates against qualitative change.

Essentially, Marcuse argued that advanced industrial society provides enough comforts and apparent 'luxuries' to pacify the proletariat, who become so alienated they are no longer even aware of their alienation.

Thus the workers are no longer the revolutionary class, and the only people who can provoke change are the 'substratum of the outcasts and outsiders, the exploited and persecuted of other races and other colours, the unemployed and the unemployable.' Most notably in the 1960s, this was taken as a call to arms for the people of colonial and post-colonial nations, and left-wing students who had lost faith with both social democracy and Stalinism.

One benefit of this is that Marcuse's most famous book, One-Dimensional Man, was extremely popular, so if you're interested paperback copies are really easy to find