Realistically, the new guy is the manager. His managers put him in place because they thought he was the best for the job. Perhaps for reasons we don't know about, perhaps they are incompetent or perhaps they think he is the best thing since sliced bread and he misled them.
I appreciate your exception 'if you have a reasonable company culture' but the truth is that of the ones that do, some of it is faked and I think the likelihood of bringing their failure to their attention and having them appreciate it is actually quite low.
If I thought somebody was listening in to my private conversations I might start having false private conversations and see if they pick up on that. If they do then that might be a crime of its own.
It got unpleasant for awhile, but I was fortunately able to move to another group and watch from afar as the sandcastle she and her paramour had created crumble around them. They were both asked to leave at the next round of layoffs.
If it goes badly then it is time to start looking for a new job. But if you have a reasonable company culture then it shouldn't do. This is why employees (even senior ones) have managers.