I read your sources, and one, as a user, I'll let these people sort out their drama among themselves, two, the security issues of the apps that are downloaded I think are way higher potentially than the ones in F-Droid in itself. With these considerations, F-droid is fine as a way of installing apps. Just as fine as any other technically imperfect service, business, or product that we use daily. In fact, I consider it higher than average in quality.

Could you elaborate on that? Do you mean bigger possibility of apps containg malware or what?

Why is it insecure?