Not everyone can be a cutting edge researcher or a successful singer/song writer. Some people are bound to be stuck in jobs they don't like, and which don't allow for any form of self-fulfillment.
Even in an ideal society where "From each according to his ability, to each according to his needs", there will still have to be some grunt work that nobody wants to do, and which the least accomplished members of society would have to take up in order to free up the doctors, engineers and artist to do work that benefits society as a whole.
This is true in our day, despite all of our advanced technology, and was even more the case back in Marx's time. It will be true for quite a long time, until some future point at which super efficient AIs and robots do all there work for us (assuming this happens at all).
How would a Marxist deal with the fact that some alienating grunt work is inevitable, even in the most egalitarian worker friendly socialist system possible? How would the people to who it falls to perform this work be able to actualize themselves?