The challenge is a small javascript program that checks the execution environment is consistent with a real browser. For instance, if your user agent says it's chrome, but it's missing features that'd normally be supported by chrome, it'll fail you. The OP mentioned "heavily customized Firefox config", so he might be doing stuff like this that makes his browser look suspicious.
From website perspective, yes. GP is likely using extreme ad-blocking and/or coming from regions where tons of bots and/or unwanted traffic are also from. In those cases, some/many human users could be misidentified as bots with little incentives to website admins to rectify.
Sadly, we probably all are LLMs/bots on the internet at this point, just talking to one another. The real humans have all become fed up and are now mostly off fishing by a lake.
