funny post.
Buying players is not and never has been an exact science. There is not a club, a manager, a director of football in history who has got every signing right, why? because there are too many variables.
You can scout players, you can research their background, you can find out about their educational achievement, you can speak to people who know them best and you can speak to players who have played with and against them.
Then you can make a bid for a player, the club the player is at may value them far more than you are willing to pay, but if you believe you have done your homework and the player potentially suits the squad you may meet the selling clubs valuation. However that does not mean the player settles into his new club, he may be unhappy he was sold, he may be unhappy his children have to move schools, his wife might not like the new house you move to, you may not get on with your new team mates, your team mates may resent your purchase and be concerned about their position in the squad. They may think Manchester is cold, it rains too much, the shopping is rubbish, its far from home, the food is crap. The area they move to may have awful neighbours, they might not like driving on the other side of the road, there may not be direct flights to their homeland.
Footballers believe it or not are human beings, they have the same hopes and fears as normal everyday people do, because after all, they are here to do a job, they are not here because they love Manchester City (although that may follow)
Mendy could have been a world class left back, but he suffered injuries and is now in court, Cancelo moved from Italy and struggled to adapt, because living in a foreign country is hard, there are different laws, there is different money, different customs, as Ian Rush said when playing for Juventus " its like living in a foreign country"
When you take all these aspects into account it is surprising 1 in 10 transfers actually work out not 9 out of 10, because some characters are made for it, some are not. Some may be outgoing and willing to learn , some may be introverted, shy and frightened, because they are human.
Over the years there have been hundreds of failed signings for every club in the country, no club always gets it right, Tkiki's record is decent, he has got some wrong, he has got some right because Tkiki is also human and he will have flaws and his judgement will not always be perfect, but to be so dismissive of the job he has done in my opinion smacks of a total lack of understanding about how difficult the job is. City have 1000's of players on their scouting database and to get it right every time has to be virtually impossible because of the variables.