Brave uses Chromium code, but it is not a Google product. And I believe you are conflating security and privacy. The Chromium codebase is in fact more secure than Firefox in many areas. There is only so much hardening you can do security-wise before you are limited by its codebase. From a privacy perspective, though, you can definitely make the argument against Google. Brave, however, removes/replaces most of the Google stuff.