I had a similar issue where I wanted to read a newly-followed blog from the beginning instead of the point in time when I started to follow, so I created https://refeed.to/
It depends on how you want to use your notes. If you're looking for a way to store information for later retrieval then what you described will probably work great. Zettelkasten is more about discovering connections between ideas that were not immediately obvious, and creating and discovering new ideas as you work with your notes.
If you allowed me to import an OPML file to get a sense for how this would work for my feed I'd check it out, but requiring a login before I can do anything real is kind of a non-starter.
You seem to be lumping conservatives and libertarians into the same group, but I think that's a mistake. I agree with your description as it pertains to libertarians, but conservatives tend to recognize as Christians who recognize certain deficiencies of humans and look to a higher power as a source of rule and law.
I think a lot of this comes down to feelings if insecurity and fear. It's much easier to vote for values over greed when you feel you have all of your needs met. But I think globalization expanded and highlighted the wealth disparity throughout the world, and seeing people that have vastly more than you can make you feel vulnerable. The vulnerability slides into fear and anger, and then you're more willing to vote for the strongman with questionable morals who's promising to do something to allay your fears, even if it's at the cost of the democracy.