I don't think your website is participating really. There are a lot of posts describing this opt-out but none really say what you are opting out of. It seems t

I don't think your website is participating really. There are a lot of posts describing this opt-out but none really say what you are opting out of. It seems that the content of your website may be used to identify the users interest. It isn't illegal because the browser is allowed to do whatever you want with your website. This is really no different than an extension that can access your website content to recommend other pages you may be interested in. In the same way it isn't clear to me why I would want to opt-out. I guess it is 1. Sending Google a signal and 2. Protecting users from themselves? But if I want to protect users from themselves I'm probably better off showing a banner recommending Firefox. (And this also helps the open web at the same time)