This is indisputable. Look at it from another angle. Let's say you're a farmer who's worked his whole life tilling fields. You've got sinewy muscle and low body fat to show for it.
Suddenly, you receive farm machinery and automated processing of your harvest. In time, what do you think will happen to your muscles? They will atrophy, get smaller, weaker, softer….because you don't use them like you used to.
The same thing will happen to our brains and our critical thinking skills when technology handles all the cognitive work for us.
Great, you say, now I can relax and enjoy my hobbies without needing to work.
Ok, sure, for a while you can do that, but you do it on borrowed time, because eventually you and the rest of humanity will lack the brainpower to keep the machines running. Or to even keep the lights on. The machines will become like magic to your cognitively crippled descendants; black boxes of mystery and awe which no one can repair or maintain.
Like the former farmer with atrophied muscles suffering from diabetes and cardiovascular disease and other ailments of disuse and wastage, you will be afflicted by brain wastage, until hardship returns with a vengeance.
And if you're really unlucky, the machines will advance just far enough to avoid the Human Regression Trap and not need human oversight anymore. Then the machines may decide humanity is an albatross.
Wall-E covered this topic really well.
