You can use SUMMON to simplify your search for movie reviews. You can limit the search to "reviews" on the left side of the Summon search page.
Dartmouth Users: Using Summon from off-campus? You'll need VPN for access to full-text.
Except for the Screen Studies Collection, the list here highlights resources that may not have citations prior to 1970. If you need information for movies made before 1970, look at the tab above called Researching early films.
These resources will lead you to more scholarly reviews.
Readers' Guide Retrospective does provide early film coverage, but only for popular literature. Popular literature includes Time, Newsweek, Rolling Stone, Cosmopolitan, Instyle, etc.
When searching, you can limit your search to "film reviews" in Document Type.
You may have your own favorite sight for online reviews. This is a list of possibilities.