Just because a method of assessment became easily spoofable doesn't mean we should give up on it. Imagine if in the era before HTTPS we just said that the internet won't be really viable because it's impossible to communicate securely on it.

I still feel like AI detectors would work well if we have access to the exact model, output probabilities of tokens, We can just take a bit of given text, and calculate the cumulative probability that the AI would complete it exactly like that.