We can't, and neither can the machines that people build and/or use for "detection." Everyone in this thread also needs to recognize the entrenched differences between secondary educators, who have wholeheartedly adopted AI products into their teaching workflow, and tertiary educators, who have adopted them only by necessity. "By necessity" in this case means "having to spend a ton of time dealing with, talking about, and learning about this nonsense."
The discourse around "cheating" with these products has always been a mistake. We should have characterized them less as "cheating machines" and more as "expediency machines." Because once you're invested in describing students as having academic dishonesty issues rather than skill issues, you've made it an administrative problem. You never come back from that.
For mine, we lost the issue long ago when accountability culture won. We should never have bothered with the idea that "mechanics, grammar, and proofreading" should be part of a "rubric" that "assessed outcomes" for "good writing." We should have just said "we don't care if you don't think this is worthwhile, because your time is worth nothing." The last two years of student labor certainly suggests this.