Let's start with this written statement: “Let him who speaks against the truth concerning papal indulgences be anathema and accursed.”
It was written by Martin Luther in his 95 theses. Read 2 Corinthians. It can be said of it that it's about raising funds. We read that God loves a cheerful giver. The Bible also mentions that those who cast bread upon the waters receive more in return. Then, as you mention, there is simony.
Let's bring this forward to US elections. Can you give to a candidate for his campaign? Absolutely. It's considered a good thing. Can you give to a candidate to buy his vote? No. That's considered really awful. Should the bottom line be, No more campaign contributions!? Someone may be trying to buy a vote!
The same thing can be said about giving to the Church. Can you give for the good of the Church community. Yes. Can you give to buy something to benefit oneself? No. The Church can give indulgences; the Church may not sell indulgences. Where does the line blur?
Indulgences can open up the graces spoken of throughout the Bible, that one cannot give to God without the result being God pours out his gifts in return. On the other hand, one cannot buy anything from God--that's not how it works. Giving versus buying: Giving is good, whether indulgences or campaign contributions. Buying, bad, whether it is indulgences or buying votes through campaign contributions.