I think that Leszek Kolakowski in *Main Currents of Marxism* best summed up the contradictions at the heart of Kautsky's politics;
"Kautsky's position is also ambiguous as to the relation between reform and revolution. At first sight he appears in general to follow Marx in holding that there is no contradiction between the prospect of revolution and the policy of fighting for reforms; social progress, the shorter working day, greater prosperity for the workers, and democratic rights enabling them to defend their interests collectively, are all ways of developing class-consciousness and training the workers to take over the state in due course. But the consistency of this position is only apparent. The real question is whether reforms are *only* of value in relation to the coming revolution, or whether they are also valuable in themselves since they improve the lot of the proletariat. Kautsky took the latter view, holding that the intrinsic value of reforms was quite consistent with their value as an instrument of the revolutionary struggle. The course of practical politics, however, was to show that this supposed consistency was an illusion. A party which treated the struggle for reform seriously and which was successful in its efforts naturally became a reform party, its revolutionary slogans surviving only as embellishment. Kautsky was able to show that there were cases in history when the class struggle had intensified although the lot of the exploited workers was at the same time improving. But he was wrong in thinking that the improvements obtained by the working class through economic pressure were, as a general principle, without effect on the sharpness of class conflict and the state of revolutionary ardour. No doubt revolutionary situations are always the result of an unexpected coincidence of many circumstances, and better conditions for the workers do not rule out such situations *a priori.* But the practical difficulty is that a party which works for reforms instead of for revolution, which achieves reforms and therefore treats them as a serious objective, will find that its revolutionary theory becomes atrophied, and when the moment for revolution arrives the party will be incapable of seizing its opportunity. The objectives of reform and revolution can be reconciled in general doctrinal formulas, but not in social and psychological reality. Hence a socialist movement that achieves success in the economic struggle and in reformist endeavours tends inevitably to turn into a reform movement. As Bernstein saw but Kautsky did not, the achievements of German social democracy meant that it virtually ceased to be a revolutionary party."
https://books.google.com/books?id=qUCxpznbkaoC&pg=PA399