There are two main limitations of the core Search module. First, it is not appropriate for very large sites -- if you have a large site, look into other search technologies like Apache Solr. Second, the Node search page type only supports exact keyword matching, which is not the behavior that most users will expect. You can improve this by installing a language-specific stemming module for your language (such as <a href="https://www.drupal.org/project/porterstemmer">Porter Stemmer</a> for American English), which makes it so that, for example, a search for the word walk would match pages containing the words walk, walking, and walked.