I don’t care if a Linux distribution offers proprietary applications or not. I just want to be able to filter it out, and that they offer open alternatives first.

More often, it's not applications, per se -- it's things like video codecs and drivers.

And there is no open-source alternative, because the only way to decode that proprietary video format or run that proprietary wifi module is to use their proprietary software to do it. So you either have user-friendly distros that include the availability of those things for the 'it just works' experience, or you have open-source purist distros where you can be proud of being purely open source, but some of your video files won't play, and your wifi doesn't work.