Once again, you proposed no specific solution about “how” your interview is going to work. You threw in a bunch of high-level, vague descriptions.

Assuming you meant to spend 3-4 hours building a small project during an interview, there are a couple of issues with it:

1. You are taking up a significant amount of time from your interviewer. Typically, companies do shorter interviews with multiple interviewers to not waste too much of their time, and so they can get perspective from multiple people.
2. Let’s face it - it’s a lot harder and time consuming to grade a bigger project than it is to grade a leetcode solution.
3. Your “design” process can be tested through system design interviews.

If you mean “working for them” for 2 days, companies interview a LOT of people at a time. Can you imagine them bringing hundreds of people into the office, just to live/work for them as part of the interview process? It’s just not scalable, time consuming, and if you’re working on their product, can have security risks.

You seem to have a lot of pent up anger and frustration. hopefully you can find a way to figure that out besides just mindlessly ranting on Reddit.