Crying "opt-in" to every single little thing that has ever tracked you for non-nefarious reasons completely detracts from the cases where tracking is nefarious. Homebrew is not tracking for ads. They are not tracking for anything worth selling to a 3rd party. They're not - and are incapable of - linking this to any other database that does contain personally identifiable information. There's no "profile" worth anything to anybody except the developers, who are trying to get some very basic information completely detached from any identity.
>> You will be notified the first time you run brew update or install Homebrew.
>> to opt-out of Homebrew's analytics you may set HOMEBREW_NO_ANALYTICS=1 in your environment
They went to the lengths to document this. And to notify you when you run the software. You have the opportunity to opt-out of something that is completely harmless. There is no valid reason to be crying foul over this. Of all the tracking that goes on with our internet connections, this should by far be the least of anyone's concerns.
I have uBlock Origin installed in Chrome. With all the ad networks and analytics scripts blocked. Google Analytics does not run in my browser. And yet, I am not even slightly opposed to homebrew's use of it. It's actually anonymous, unlike how many developers use GA in the browser (tracking IP addresses, custom fields like user ids that link back to the site's database, etc). God speed, homebrew devs.