Some things to keep in mind when searching for film reviews:
Film reviews are published around the same time as the premier of the film. Knowing the year of premier can help make searching easier.
It is pretty easy to find film reviews via database, the library search, or the internet from the last 30+ years. For older reviews, you may have to widen your search and resources.
If you are not sure of the film's title, search with other information relevant to the film such as using the names of actors, directors, etc.
Founded by the University of California Berkeley Art Museum & Pacific Archive, CineFiles "contains scanned images of reviews, press kits, film festival and repertory theater program notes, newspaper articles, and other ephemera from our extensive collections."
Letterboxd is "GoodReads" for movies. Track movies as you watch them and rate them and share your opinions with others. Letterboxd is a "global social network for grass-roots film discussion and discovery."