The strange part is how moral responsibility somehow always lands on the builders... the people with the least leverage... while the funders get to ask the ethical questions. Weird!
No, we don't have to take the funders' money; that's what having professional standards means. Nobody would excuse a doctor performing unsafe procedures because they "needed the money". Engineers were jailed for the Volkswagen emissions tampering scandal and nobody would excuse them for needing to take funders' money.
I agree that holding only the concrete implementers responsible would be inappropriate. However, I don't believe that distinction is made. One says "I am building a house" even if they are completely contracting the job out. I'd suggest the greatest responsibility lays with the funders and that the Pope would agree.
The funders are among the principal builders in this context. This is addressing the people who have a say in what is built, and how it is built. Much of that belongs to the executive and ownership class, but not all of it.
Mark Zuckerberg is a builder in the context of the encyclical.