Well taking into account age, experience, language barriers etc I think
“It is obvious rule that who are shit to begin with will remain shit.”
doesn’t ring true. For me.
But you are welcome to your opinion.
And a problem with selling players after 1 year is someone has to buy them.
Loans are a decent way to get around the issue if you are not sure about them.
How does language barrier have impact on inability to put in accurate cross or pass the ball upfield?
And talking about the main point - it does not mean that 100% of players who start off poorly will surely remain poor. But there are many-many more of those who remain sub-par compared to those who turn things around.
I have provided long list of players who remained dissapointing.
I can also give a long list of players who came in and impressed to smaller or bigger extent - Toby, Jan, Wanyama, VdV, Dier, Davies, Eriksen, Dele, Kulusevski, Bentancur, Romero.
And then there is a list of players who came in, were poor but turned out brilliant - Son.
So there you go, for every Son there is list of 11 players who seemed bad and never got really good + 11 players who seemed good and remained good. Even if you include Bale here, that would still be 2 for 22 - not too high ratio.
Those turnaround stories are rare in reality. I don't see why it is so hard to admit it?