You can't because you are not supposed to. Whitepapers are basically the abstract idea about the project and what makes the project good or bad or scam is how that idea is implemented. For example you can't really figure out what bitcoin potential is by reading the paper since that will only introduce the general idea about what bitcoin is trying to achieve. Not to mention that sometimes the idea is very good but the implementation is terrible/scammy like ethereum where the idea of a "decentralized smart contract platform" is good but they implemented a centralized platform for scammers with lots of protocol flaws and a mutable blockchain.
I agree with your point of view. To tell the truth, white papers are conceptual things, and I don't have a good way to filter them. In most cases, some project teams and project endorsements are seen, and then eggs are not put in one basket, and small investments are made. The essence is whether the project party wants to do evil? Or, someone forced him to do evil.