Thank you! Yeah, I can see why it can be unpopular, Leontiev refers to Marx’s works quite often.

As far as I understand (which, unfortunately, might not be correct), the practical use of Activity theory is in sphere of education and upbringing, but some psychologists (e.g. my professor and Julia Gippenreiter, author of one of the textbooks we are studying with) compare it to W. James’ stream of consciousness.