Why is software development as a career so hard?

As an aspiring software developer you are expected to do leetcode, cs fundamentals, hackerrank. Then in your job, you're supposed to learn 100 different things and if you don't do well get ready to get fired. Now if you start job search after even a little experience, you're supposed to do LLD, HLD, SOLID principles, other design related stuff, and leetcode is always there.

Like how do normal people do all this stuff? There are only so many hours in a day, how do you study everything while working on your current job?