I use those. They work on about 10% of sites, because there are about 1,000 vendors of "cookie consent modals" so nothing about them is standardized. Also, none of them that I've seen actually do anything, since "blocking all cookies set by 72 different adtech scripts loaded before and after you init" is not a real thing that Javascript snippets can even do. While most adtech snippets do have APIs to carefully pass in the user's GDPR prefs, most people don't wire them up, or even knows what order the various scripts load.