You've applied to 400 jobs and had 3 responses and no success to be blunt your option about what you need to do to get hired is worth zero.

You refuse to change anything about your process, you aren't working to improve it, you are arguing against people telling them you don't need to do common/standard things.

This thread is a pretty good insight into why you are failing and what you need to work on.

Like I said, i had a legit linkedin account before i closed it and it never felt like it did anything for me. I have changed plenty about my process, from cv iterations and reviews, ai assistance to cater to job posts in cv and cover letters, etc. Of course i think all the information is great, but i also have first hand knowledge and experience. If you think all that's missing is a furnished LinkedIn account then i can tell you that it isn't accurate - in my experience.