I think it is perfectly correct that politicians should NOT hold shares, or even work for that matter, for in any media company. In any country. The UK has rules that limit political parties from owning some forms of media shareholding for example!
Media-ownership-rules-report-2018.pdf (ofcom.org.uk)
If they don't own shares or work for the media then it is one less way that the politicians can be accused of using their "financial power" to influence the media!