I don't see how they could've possibly made it worse. It'll compress your headers and maintain their load order (which is important) as much as possible. This significantly reduces load times in all our tests (we're using this on our site). The lazy loading of images especially provides significant gains.
It sounds like your issue is with your server it self. There's no reason for something as small as Bootstrap CSS or Fontawesome CSS causing your site to be slow. If it's the JS then it's not CB as we don't use JS for either of those. You're welcome to provide a URL to a slow page and can take a quick look, but we don't typically assist with issues like this.