The problem is they don't know how to actually compile and run a "Hello World" program, or write and run any kind of program on a physical computer, because they never had to do it as part of their computer science education.
Real tech interviews have always been about understanding and applying data structures and algorithms, with some emphasis on problem solving with those tools.
A really long time ago, there used to be questions that were more like "do you know some very common C/hacker idioms", like write a one line strlen or reverse a linked list in place. I used to get asked stuff like that in the late 90s.
(There were also the brainteaser style things, like how many golf balls fit in a 747, but those were often for non-programming roles where people were looking for your ability to problem solve in a vacuum with little information. Those were rarely aimed at engineers, but at engineer adjacent non-technical roles.)
Isn't it the foundational concept of fizzbuzz that a lot of applicants to programming jobs are "completely unable to do anything"?