Russell wrote a good essay on his thoughts about communism and Marxism as a non-Marxist socialist. [0]

e.g.

Some lines of note

> The theoretical doctrines of Communism are for the most part derived from Marx. My objections to Marx are of two sorts: one, that he was muddle-headed; and the other, that his thinking was almost entirely inspired by hatred.

and

> I am completely at a loss to understand how it came about that some people who are both humane and intelligent could find something to admire in the vast slave camp produced by Stalin.

You say

> Sartre repellent on multiple levels

IMO the group of French intellectuals influenced by the Nazi philosopher Heidegger (of which Sartre is certainly one) looks increasingly creepy the more you look into them.

[0] https://www.rjgeib.com/thoughts/opiate/why.html The rest of the page looks a bit crazy but that's the first google hit and they host the whole thing in plain text.