I beg to differ, and if you see other sellers' reactions you'll see that they also feel the same way, not just me. We KNEW before the exact reason for upgrades or downgrades because there were a couple of quantifiers, Order competition rate, minimum rating and response rates were not something complicated as things are now. just some extra parameters that we don't know how they work or change does not mean transparency.
Generic advice like sell more, do more are good in theory, I had a LOT of orders with repeated clients with good reviews after the new system but my success score stayed at 6. Optimism is really good but you can't use it to cover the ongoing flaws, that's a recipe for disaster.
Just don't see it as MY problem, try to see how other sellers are affected and how they are feeling, and then you'll realize it is a real thing.