Checking "I'm not a robot" is the easy part; even if they randomize the name/id, you can still do it using
document.querySelector('css selector for the checkbox'). You can even add a rule below to auto-click the submit button to automate everything for you; then use the Site filters to automate everything for each page (e.g., this way you an automate the entire store checkout process).
The one CAPTCHA that you'll never be able to "autofill" is the one that shows a bunch of images and asks you to select which images contain a tree, etc.