I tend to disagree. Hacker Rank and Leetcode test a very specific set of problems — ones you’ll see in a coding interview. While that has its own value in getting you a job, I’m not sure it’s helpful in the real world.
To be clear, the Project Euler problems on their own aren’t super useful in the real world either. There aren’t many times when you’d need to calculate the sum of primes under a given upper bound, for instance. However, I think I made a good case in the article for why fundamental problems like this teach you a toolset that’s extendable to real problems, especially optimization intuition and groking a language’s syntax.
Hacker Rank and Leetcode feel like a system to teach you to memorize coding interview questions. Project Euler problems with their variety make sure you deeply understand the fundamentals of storage, manipulation, and computation complexity.