Sadly in the new market I fear they're right - the only 5*s that do appear come from managers selling. And the "bug"(or feature) that makes 5*s only appear in the final 10 minutes means that people struggle to buy, which then means they don't sell to the next level down
In the old market having some extra good 5* players generated meant people bought, then offloaded their old guys. Also the offloaded players were visible in the market for longer, encouraging buyers.