There’s a lot of runway left for obstacles that are easy for humans and hard/impossible for AI, such as direct manipulation puzzles.
That's irrelevant. Humans totally hate CAPTCHAs and they are an accessibility and cultural nightmare. Just forget about them. Forget about making better ones, forget about what AI can and can't do. We moved on from CAPTCHAs for all those reasons. Everyone else needs to.
OK, what you now call turnstyle. If I get one of those screens I just close the tab rather than wait several seconds for the algorithm to run and give me a green checkbox to proceed.
That's irrelevant. Humans totally hate CAPTCHAs and they are an accessibility and cultural nightmare. Just forget about them. Forget about making better ones, forget about what AI can and can't do. We moved on from CAPTCHAs for all those reasons. Everyone else needs to.