You make it sound as if the only ego that need to remain in check is that of the existing dev team. That is really wrong. It’s more important for the new dev to check their ego at the door. Its exhausting when a new dev joins a project and you suddenly have to rehash all of the architecture decisions made months ago. Especially when it’s is obvious that the newb hasn’t yet taken the time to understand the existing system. Learn how things currently work before you start proposing changes. Without that research first you have zero credibility. If you are joining an existing project the balance of effort to adapt is on you not on the existing team.