From what I've seen, i think his strength lies in observin rather than directly commenting on things. His films are very dependent on the visuals. The editing often seems confrontational to me, not smooth or invisible as in classic hollywood. I'd say that he wants a response by the viewer to his work, and one that doesn't end after the film. Critical of society. I'd say closest to Doillon, despite the fact that he doesn't use dialogue too much, the atmosphere is often similar, and the characters are usually outcasts or outsiders, always people between two states, lpassing from one to the other.
But of course he has worked about 40 years, so you won't be able to get a "complete" picture, but rather different periods. But I've seen very little, so others have surely more to say.