You literally can get good at leetcode with an hour a day for a couple of months provided you studied computer science or even just like took AP Computer Science in high school. And even that just requires an internet connection.
How do you not understand that many people with families or other external obligations wouldn’t have the luxury of spending 7 hours a week for multiple months on leetcode?
Like everything else, it's an opportunity cost. Personally, I think LC is a great return on time invested. It takes far less time and money than say, any of the traditional gatekeepers, even for example a CS degree, or even perhaps a good data structures and algorithms class that is semester long.
If they need to spend that level of time in order to do a few search or sort problems on a whiteboard I'd be concerned that they don't actually know algorithms or datastructures.
The kinds of questions most companies ask are not hard.
I am 35 years old and never even heard if a high school computer science course. I spent one period of my last semester assisting the network admin with maintenance tasks, which was the closest thing we had to AP computer anything, and only 2 students in my class had the privilege.
You literally can get good at leetcode with an hour a day for a couple of months provided you studied computer science or even just like took AP Computer Science in high school. And even that just requires an internet connection.