I understand your comment is a flippant, off the cuff remark on some internet forum, but there is truly no worse advice you could give a first-time employee, than to encourage them to think of themselves as equally valuable to their coworkers.

They aren't.

And their job is - solely - to execute on the work that their managers give them.

As they settle in to the new role, they will learn how things work in the organization, learn who welcomes feedback and initiative, and who doesn't. They will be invited to participate in discussions and designs when they have shown an agility and capability to complete their assigned work.

As someone who has hired/fired countless people, if I make the decision to hire someone for their first job, I am going to give them a very narrow band of responsibilities that I am sure they can accomplish. I am going to make sure they work, work hard, and produce quality output on a consistent basis. The reward for doing so is greater responsibility and my soliciting their input when I see their input might be valuable or insightful. Over time they will grow to be a valued collaborator.

But if one of these flunkies speaks up in a meeting and posits a half-baked idea in front of a client or manager, that makes ME look bad. Now I gotta crush the kid's idea, in front of other people, who are thinking, "Who is this kid? Why did they even hire someone with such dumb ideas?"

Well, I DIDN'T hire them for their ideas. I hired them for their facility with Photoshop, or Illustrator, or Ruby on Rails. Not for their high-level concepting or design capabilities, since they have none.

So yeah.

I realize this is a strong reaction to a posting on an internet forum, but OP was looking for good advice on their first job, and your advice did not meet that need.