Admittance to the Euro Club comes with certain principles, ideals and shared valuess.
What has happened in Polands's case, is that the law has been changed to facilitate the States interferience in the free media. The State has given itself the power to remove anyone who does not follow the party line. It is a totalitarian law and one which does not fit in with EU or any democratic view of freedom of speech.
In essence, Poland was admitted to the EU because it conformed to certain entry criteria, but it has now changed its laws and now does not fit in with the rest of the EU.
If the entry rules were rigid and and unbending, that would be a problem, but they are not. The principles are fairly loose and undefined. However, a state run media that removes free speech in a member nation crosses that line. The fact that the law has been changed to make that possible may mean the law is not compatible with membership of the Euro Club. If Poles wish to return to the Soviet era of State Control, they should perhaps leave the EU first.