“At best you can find are vague suggestions (pay bills on time, lower credit utilization, lower debt to income ratio, increase net worth, etc.) with no real calculation on how much each of these impact the scores or if other factors are included in the real calculations. “
The percent of each factor is not a secret. Here are the typical percentages.
https://www.myfico.com/credit-education/whats-in-your-credit-score
Take “Amounts Owed - 30%” - Credit available vs credit utilized. My experience is the score changes when you move from one 20 point boundaries to the next, for better or worse. 20%, 40%, 60%, 80%. So if you pay down a card and your available vs credit utilized goes from 40.5 to 39.5, expect a small score increase. They’ll never give precise details like this so you can’t game the system. Bankers want the score good enough, but not too good. The higher the score, the lower the interest rate and hence less profit.
Or as the myfico article you posted states it:
Your FICO Scores are unique, just like you. They are calculated based on the five categories referenced above, but for some people, the importance of these categories can be different. For example, scores for people who have not been using credit long will be calculated differently than those with a longer credit history.
In addition, as the information in your credit report changes, so does the evaluation of these factors in determining your FICO Scores.
Your credit report and FICO Scores evolve frequently. Because of this, it's not possible to measure the exact impact of a single factor in how your FICO Score is calculated without looking at your entire report. Even the levels of importance shown in the FICO Scores chart above are for the general population and may be different for different credit profiles.
They want us to use a kind of fuzzy math and sorta/possible/maybe set of rules regulated by the government in hopes of getting a credit score dictated by government FICO regulations in important life-determining choices like interest rates on homes. Yet I would have failed every one of my math courses I took getting my computer science degree if I had used that kind of vague math. To me that's the government regulating money decisions of our lives without telling us how they're doing it.