Degrowth is just a technical term for decoupling our goals from constant GDP growth, which is basically mathematically essential for dealing with the climate crisis in the global north. There is nothing in it that is inherently idealist or incompatible with Marxist-Leninism. It is a policy goal, not a theory of how to achieve the goal.

The current issue of Monthly Review is a double-issue on degrowth and there's a lot there, I recommend you check it out.