The amendment says that the government has to stay out of the way.
The First Amendment isn't the sum total of American law. I'm not a constitutional lawyer, but I'm pretty sure there are constitutional powers meant to provide effective democratic elections.
The tension here is between those two interests. I think it's worth considering the idea that a too-absolutist interpretation of the First Amendment (in regards to spending) may interfere with the nation's ability to provide effective democratic elections. Both are important priorities.
Also, it's not like the Constitution is perfect, timeless document. If it doesn't do enough to ensure effective democratic elections in light of its other provisions, then changes should be considered to fix that oversight.