no it doesn't fail. Agents are very good at comparing traffic characteristics from a real browser and a headless/automation browser and getting it to behave in the same manner. It's a cat and mouse game for sites stopping unauthorized access but right now llm agents are ahead.

For testing proxies should be used to avoid IP ban issues but given enough time modern agents can figure out how to bypass most of the modern scraping/automation prevention mechanisms.

I have built and used a lot of different automations and web scraping implementations for my business and it's never got permanently stuck yet, some take a bit longer, some shorter, but all within a reasonable time with little external help they have succeeded in their tasks.