Apple also has a big enough marketshare to matter to the DMA.
Maybe the EU can ask Google to open Chromecast up so Apple can integrate it into iOS. Then you can use it from any app without needing special integrations.
You are comparing Apple's primary product/service against a throwaway part of Google's. Google has walled gardens around its primary business too. But they are so deeply ingrained into our world that nobody questions it, because there's also no viable competitors.
Criticism of Google is fair, but it has nothing to do with excusing Apple here.
Because with Android devices you can sideload any app, alternative stores, you can set any 3rd party app as default, they can handle pretty much any type of file, etc...