It's improved with age and the fact that Fincher's style became accepted. Once it did, and Fincher became successful people were more willing to give it another look.
Alien3 isn't a bad film by any stretch. There's some great work by Weaver, Dutton, Brown, Webb, plus Norman Reynolds, George Gibbs, Terry Rawlings, Bob Ringwood. Even ADI, who's Bishop puppet was phenomenal.
However it doesn't really compare to the more accomplised efforts of Scott and Cameron.