Well, I agree. Marx alone won't help to understand the world today and in the future, but he is nonetheless an important theorist of capitalism. That can be fruitful for certain principles or ideas he ventured into long ago and that can still be useful or form the starting point for an analysis. Marx as social scientist might be doged by todays social sciences, but I guess the Marxian itch is that materiality determines these social sciences, while they think of themselves as an rather autonomous enterprise in the (dynamic) scientific system that came into being during the last centuries. In that way Marx was handling question of epistemology which is a tricky question for science, since it becomes a hall of mirrors, self referential paradoxy.
Marx is a critique that works with suspicion. What seems natural to us, even of divine nature is called into question. Marx is still part of the enlightment "project" in that regard. Perhaps the necessary step to push enlightment further, to actually push it through (I think Adorno also that something along the lines about his conception of enlightment together with Horkheimer).
Today so many knowledge (also empirical knowledge) and theory can be brought into what Marx started. A lecturer told me that (nearly, I should add, as there are some orthodox marxists) nobody, who read Marx, thinks that Marx would be sufficient in grasping what is going on.https://www.upress.umn.edu/book-division/books/the-deadly-life-of-logistics
This book I imagine (did not read it, just on my list) can be useful in understanding global capitalism, it can be brought into fruition with Marxian thought I guess, in what way I cannot say, but I'm sure that many studies can be integrated and update Marx so to speak. Marx was not able to give detailed analysis of certain/every area. The question of technology (as "standalone" or in relation to the human, but also enmeshed in capitalism, but also in other regards, there are many..), which I'm interested in, has been tackled by Marx, it can be fruitful, but it would also be crazy to just rely on Marx in that regard today.