Hardware

This is largely a philosophical question that everyone must answer for themselves. There are a few arguments that can be made and they have all been made many times in the past. Some people will say they define freedom as the ability to use their hardware to it's maximum potential and run any application they want and just have that work. One potential weakness of this argument is that if you take that to it's conclusion the best OS to use would be Windows. Another type of argument could be that freedom means the ability to control, audit, change, and share the software on your machine ( just paraphrasing the four freedoms : https://www.gnu.org/philosophy/free-sw.html ) if this is your view it means the only software that makes sense is fully free software and free OSes. Still another approach that could be taken is that the ideal is fully Free Software but compromise at times for cases of usability and in certain areas where you disagree things should be free. For instance if your computer doesn't work at all then you can't really do much to support the free software movement. In that case you may decide that a OS with some non-free elements is better than nothing. Or maybe you don't think artistic works like Games need be free. There are black and white approaches there are nuanced approaches. I think as long as you are informed and make a decision from a place of being informed no one can really blame you for the decision you come to.

As to the technical limitations there is really no one saying "You can't do that" you can install whatever repo you want to download any package. You could recompile and install a different kernel with the binary blobs if you want. What a system like parabola is doing is saying that they understand their users don't want those things so they are not installed by default. It's not a "You can't do that" it's a "We strongly recommend against you doing this". If you installed a typical distro you could waste weeks trying to remove all the non-free elements. So a distro like Parabola just makes that part frustration free for the people that want it.