The ending of A Clockwork Orange isn't changed, exactly. Kubrick was working from an edition of the book that had the final chapter censored for some reason.
Very well, it differs from Burgess's unabridged version.
I haven't read the book, but I have read summaries of that final chapter, and it strikes me as a cop out.
Not really fair to judge without the context of the entire work, is it? One could as easily say that the film is a cop out, giving meaningless violence an aesthetic appeal that is absent from the book.