Hey... I agree that THE LOST WORLD is piss-poor when graded with those other films. And JURASSIC doesn't touch JAWS either. But I still find values about each of the films to warrant fun repeat viewings.
However... I don't think at all that his abilities are on the decline. In fact, 3 of his last 5 films are arguably among his very best. Only JAWS, RAIDERS, CETK, and (maybe) ET are on par with SCHINDLER'S, AMISTAD, and PRIVATE RYAN. How can he be at a "decline"?
If you ask me, he's at his peak. The problem is that he seems to decide for himself whether or not he's going to put his heart and soul into a film. To look at LOST WORLD and AMISTAD and know that the same man made both films in an 8 month span is mind-boggling. I agree with you 100% there.