Searching the Web is so easy and immediate; it is often the first place we look for information. There is a lot of invaluable information on the Web, too, including primary source documents, current news stories, images, government reports, and more.
Using the Web to find literary criticism is problematic. To quote the Library of Congress: "Although some literary criticism can now be found through the free Internet, the vast majority of scholarly criticism is still found in print or through subscription databases accessible through libraries."
There is simply not a lot of literary criticism freely available on the Web, and what IS there is often produced by students and/or enthusiasts who lack the proper authority and credentials to use as sources for academic work.