Our general attitude to Marx is that he was a pioneer Socialist, the one in fact who put socialist theory onto a scientific basis. We accept his labour theory of value, his materialist conception of history, and his view that Socialism must be the outcome of the political struggle of the working class to free itself from capitalist exploitation. We therefore sometimes call ourselves "Marxists", despite the shortcomings of this term (such as suggesting that we might regard Marx as some infallible source of wisdom who never made a mistake).
But we are not committed to applying socialist principles in precisely the same way as Marx did a hundred years ago. This is because conditions have changed considerably since Marx's day. When he was politically active the workers were only just beginning to organise politically and industrially. He considered it his task to encourage this, even if the organisations the workers first formed were not explicitly socialist in character. He expected, somewhat overoptimistically as it has unfortunately turned out, that the workers would soon move on to become conscious Socialists.
In Marx's days the world political scene too was different. Capitalist Europe (those countries in which the bourgeois revolution against the landed nobility had taken place) was threatened by reactionary feudal powers, especially Tsarist Russia. Opposition to Tsarist Russia became something of an obsession with Marx and led him to take up positions, such as supporting the British-French-Turkish side in the Crimean War, which we have no hesitation in saying were wrong. Generally, what Marx favoured was the further development of capitalism since he knew that this would ultimately remove the threat the reactionary feudal powers posed.
He was proved right in this. The first world war (aptly named as it marked the final triumph of capital¬ism as the dominant world system) saw the end of the last great dynastic empires of Europe, not just Tsarist Russia but Imperial Germany, Hapsburg Austria and Ottoman Turkey as well. Since then capitalism has clearly been the dominant world-system so there is no further argument for socialists to favour capitalist development in order to undermine feudal-based regimes. This has been done, and Socialists can now concentrate exclusively on undermining capitalism by build¬ing a world-wide movement for Socialism. In this sense developments since Marx's death have made his tactics (but not his principles) outdated.
These same developments have also made it possible to establish a society of abundance, with from each according to his ability to each according to his needs, now without any transition period while "the forces of production are raised". The forces of production have already been raised immensely since Marx's day: Why, Marx lived in the age when road transport was still by horse and carriage and before the electrification of industry, let alone the discovery and application of electronics and nuclear power! The wonder of his age was "the electric telegraph" while we are now only a few decades away from the peaceful use of nuclear fusion which would give mankind an almost unlimited supply of energy which could be used to produce wealth in abundance.
To be fair to Marx though, he would have been the first to admit this. As he and Engels wrote in a preface to the 1872 German edition of the Communist Manifesto:
"The practical application of the principles will depend, as the manifesto itself states, everywhere and at all times, on the historical conditions for the time being existing, and, for that reason, no special stress is laid on the revolutionary measures proposed at the end of Section II. That passage would, in many respects, be very differently worded today."
They went on to say that in view of "the gigantic strides of Modern Industry since 1848, and of the accompanying improved and extended organisation of the working class", and in view of the experience of the Paris Commune of 1871, "this programme has in some details become antiquated". If these measures were antiquated 100 years ago, they must be prehistoric today!
Marx, incidentally, never spoke of a "workers' state" and it was Engels who wrote of the withering away of the State. Marx himself preferred to talk about the abolition of the State. The political and economic developments listed above made Marx's formulations more appropriate than Engels' — though of course the abolition of the State will still be a consequence of the change in the mode of production.