Shitty is probably not the correct word.
Typically, a japanese talent manager is a business person. Somebody with connections, with an understanding of the media industry. They connect talents with the people and resources they need, like hiring the necessary personnel to put on a stage performance, finding lyricists to write songs, etc. In Cover's case, their managers are probably slightly more specialized in social media youtube content related skills, like google adsense, understanding the algorithm, video editing, etc. That kind of stuff.
The problem is that these people are not lawyers. They are not legal experts. They have absolutely no qualification to deal with copyright law or legal disputes in general. Rights? Permissions? Not their field. And when a businessman doesn't know the answer to a question and doesn't have the expertise to produce an informed answer, they will always tell you the same thing: "No."
No I won't look it up
No we can't figure something out
No we won't hire somebody who does know.
No we won't take risks that might get us sued
No we won't make changes to our payroll or improve our skillset so we can better handle this as professionals in the future
This is why talents are often the last people to know when Cover secures permissions. Because it's covers legal team that's actually securing those permissions (except for the few odd cases where a talent goes over cover's head and contacts someone directly). Management is just there to tell the talents "we hired you to play games, just play games" and to forcibly take their stream offline if they break a company rule. Everything else is above and beyond the call of duty, and going above and beyond, more often than not, can cost them their job.