LOVED the Abyss.......Rotten Tomatoes, not so much!
IMHO Rotten Tomatoes caters mainly to more modern and mainstream movies! If you're seeking reviews on older classics movies or those off the beaten path of yesteryear, finding some on their site is going to be few and far between! Also they don't offer nearly as much info on cast members, script writing credit, directing credit, etc etc as IMDb does for instance.
While Rotten Tomatoes may be fine as an appetite, for my main meal I'll always need to look elsewhere.......