How will the LLMs be used for this? They can't solve captchas, and they're not smart enough to navigate the internet by themselves. All they do is generate text.

Transformers can definitely solve captchas. Not sure why you think otherwise.

So captchas are obsolete now?

For a while now, even before the latest AI models. Paid services exist (~2$/1k solves https://deathbycaptcha.com/)