The problem is that many of these content are image-only (titles don't always include names), requiring some kind of extension/userscript that's able to do some kind of OCR or Computer Vision. You can block specific communities or users, but this will also block potentially good threads (not everybody that's posting about politics is necessarily a politics-only user, same goes for communities such as !nostupidquestions@lemmy.world that aggregate both political and non-political content).

While there are communities explicitly and specifically focused on politics that can be blocked outright, there's no easy way to block every single political content without some kind of sophisticated client-side AI (which is error-prone).