I file "literary critics and academics" in the same category as "movie critics" - if they hate it, it's probably awesome, if they like it, approach it with caution.
Honestly, it's for much the same reason - they're a bunch of insulated, insular, self-referential blowhards who never worked a single honest job between their collective existences.
This is completely countered by the vast number of literary critics and academics who adore Gatsby and credit it as one of the greatest novels ever written. So, again, YOU don’t think it contributes, but lots and lots of far more accomplished people do.