Critical thinking is actually something that people exercise (or don't) all the time. It is a skill and practice that is inarguably valuable in all situations. This paper is not about the effects of critical thinking on "AI results", but the exact inverse of that.
Do you value the capacity for critical thinking in yourself? In others? If so, the effect reported by this paper is probably of interest to you.
If I want to know when Obama was born, and check wikipedia and believe what it says, by their measure I am practicing less critical thinking than if I found independent verification. Independent verification is the main way they measured critical thinking. They are NOT measuring that I thought about how much I could trust the result, and decided that yes I could.
And, well, yes, they're right. But for most purposes, wikipedia is pretty credible for something like that, and it's just a waste of time to follow up on it. What's important is that my calibration is correct.
I'm not even saying I disagree with the idea that there is likely a problem here, with people offloading thinking. But I'm thinking critically about this particular study, which seems totally useless.
The example's not relevant; the two things are not analogous. Moreover your point only works if one accepts your conclusion that:
Independent verification is the main way they measured critical thinking
But they also reported assessing things about the content, like style/personality, logical soundness, relevance to a topic, or suitability for a specific purpose.
Studies don't need to justify themselves with concrete conclusions; gathering the data for future use is a fine goal.