This sounds more like an issue when it comes to interacting with those people in general, regardless of the medium. I bet those friends would still bring up their political views in irrelevant conversations irl, on twitter, or literally everywhere else they socialize.
This isn't a fault on the part of FB. You indicated you are friends with those people and want to follow their content. If you want to be friends with them on FB, but not see their content pop up on your timeline, that option is a click away. If you want more granular filtering, so that you can still see non-political posts from those people, you need to indicate to the algorithm that you want less of that by clicking "show me less posts like this", and it will eventually learn.
I see those options as a reasonable approach, as I struggle to come up with a better way to filter the content of people you follow with such granularity. The only option I can see in my mind that would work better is literally having someone work as your personal "filter", so that they can only show you the posts you want from those people. But that, obviously, is not a viable approach.
It's just like in real life. If you have a friend who you want to continue socializing with, but in public settings they say extremely off-putting things half the time that you don't want to hear, your options are to either stop socializing with them completely (aka unfollowing), to ask them to stop doing it, and that's pretty much it. All of those options are available on facebook as well, except facebook offers even more options that are all pretty good.
And I am saying this as someone who opens facebook at most once-twice a week for a little bit of time, just to check up on what my friends post and to read thru a few interesting discussions in the hobby groups I am in. If I occasionally see a wild political shitpost, I just click "show me less content like this". And the algorithm, surprisingly enough, tends to adjust to this pretty well.