Exactly this. Buying players isn't great, but it's fine; you can get mid-level players for pretty cheap. There's not really as much strategy anymore, it's just "pay whatever you want", especially since people can just jump into an auction after it has gone to the later rounds, but it's at least adequate.
But selling players is impossible to get the value you deserve for your players. It's a broken system. I will definitely quit after this season if they don't fix that, because otherwise there's no point; you just grind through players like they're nothing.