Regardless of how impressive your side project is, unless it is a very special exception (e.g. you’re head maintainer of a linux distribution or open source tool the company hiring you is extensively using and needs your expertise on), it’s only getting you into the door to talk to people, and it’s not a route around the interview process.
So, ultimately that process is going to be whiteboard coding, because it (let’s be honest) basically always is. That whiteboard coding tends to draw its questions, most often, from question pools like those on Leetcode.
This means if you’re resume’s strong enough for someone to talk to you, you probably should be optimizing to pass the whiteboard section.
Yes/No -- In my last job hunt, I talked to more than one employer who said they had declined people who rocked the whiteboarding, but had nothing else to show. People are building teams who can work together, communicate well, and dedicate their efforts to completing projects together. Good whiteboarding is a prerequisite to being part of a team... but not the entirety of a hiring decision.
Having side projects to show doesn't prove one can work together on a team, communicate well, nor dedicate their efforts to completing projects together.
a lot of technical interviews use super contrived problems for you to work through. There is a non-zero chance that a super experienced engineer could be qualified for a job, but stumble on the applied questions asked by some interviewers.
leetcode is intended to help that type of interviewee get up to speed on a lot of those sort of technical interview questions that they may not have directly thought about for years.
I think it's because such a small percentage of competing applicants are likely to have substantial projects anyway, you may as well focus on the common denominator of the interview, which are the data structures and algorithms questions.
It is like buying stamina when the next boss can be easily defeated using strength.