But if I want to quickly decide if a movie is worth watching, looking up its IMDB score is a blunt but fairly decent instrument. I'm not going to read reviews of 10 movies, usually.
Personally, I most enjoy watching reviews after I've seen a movie anyway, to get a critic's take on the movie I enjoyed (or didn't).
(I also try to avoid reviews before watching)
If it's simply to answer the question, "what will the wife and I watch tonight?" and you're presented with a algorithmically limited set of options based on your viewing habits and your up/down votes, yes, I think scores are a "good enough" blunt instrument.
If you want to explore the work of a particular director, genre, theme, period or actor but don't want to just watch all those films chronologically (or by only viewing "the blockbusters") then reading a bunch of reviews will help A LOT. The scores in that scenario would then merely be trite factoids.