That's what I don't understand. If you're building a bot to get past reCAPTCHA then you're almost certainly in some selenium/chrome headless environment, with full chrome support of cookies, Javascript, you name it. There's certain methods of detecting such environments based on their environmental variables there were again more work around to patch those.

Also the fade is irrelevant because the bot already has access to the image without the fade (although it still has to await the fades completion to continue).

The fade thing is to rate limit attackers.

By blocking specific cookies you're making yourself look like a certain kind of botnet, so obviously you're going to have a difficult time convincing the site that you're a legitimate user.

Most users don't block normal cookies, so if you go tweaking the machinery that manages the relationship between your browser and the site, then be prepared to deal with a buggy experience. This is what it means when they say that what you're doing is "unsupported." Nobody is going to spend any time optimizing for your weird setup.