They are a gatekeeper for a huge number of websites, this effectively blocks anyone from using a browser that isn't a wrapper around Blink, or Firefox itself. As it is there are very few independent browsers given Google's absolute monopoly over web standards and constant stuffing draft specs into Chrome. This is far worse than the IE6 days.

I think a more honest title would be: The “Verify you are human” checks never succeed in non-mainstream browsers.

What’s wrong with the original title: “Verify you are human” checks broken in Palemoon browser again

Not really-they don't care about this despite multiple complaints from users. As it is non mainstream browsers (having their own rendering engine that isn't Blink or Gecko) are few and far between.

It's exactly the same attitude of 'this site requires IE6' from the early 00s, but with worse results.