I totally agree with all your comments. I find I can normally see what a new player is like either before they have joined us or in their first few games for us. I reckon most fans are wishful thinkers and far too optimistic about a player's future when truth is they are just not good enough in many cases.
Olise, Eze, Wharton, Guehi, Lacroix, Munoz, all immediately very special, then current players, Hughes, Lerma, Kamada, Mitchell, Mateta, Richards, all shine some or most of the time, right from the off. There are others too.
Rak Saki never quite got there and current others looking like that. I haven't seen any in the wings with the X factor.
Vierra reckoned 2% of academy players would make it into pro football. Probably slightly optimistic.
All a bit depressing, but pro football is ruthless. I reckon you can always tell deep down when a star arrives.