Better than most is no longer good enough for any of our players. We are aiming for 'nobody obviously better'. We are nowhere near the best in Europe and we want to be the very best. That means SIGNIFICANT improvements - we've done that with the manager (hopefully), and we are doing that with the tactics and workrate (hopefully), but we can't escape the obvious - needing to do that with players too.
In an ideal world, Pep would work his magic on every current player, they'd all fall in love with City and become the new improved Barcelona and the entire would would marvel at us. Or... we could take off our sky blue glasses and say 'he's good, but not THAT good', or 'he's been a great, but it's time to let go' or 'having the skill is great, but without the workrate it's not enough'. I'm not talking specifically about Hart here, but any player. What we currently have is not good enough to win CL. It's not even good enough to win the PL consistently. Things have to change, and we'll just have to go along with Pep's judgment.
All of that said, I'm not in the 'Pep is God' camp. He will make mistakes. Ferguson did. Paisley did (though not many!), Clough did. Chances are, he won't be able to make us Barca in 3 years. But hopefully he'll get us as close as anybody else possibly could, ready for the next guy to get us closer still.
I can't type too much nowadays. But that is a good response.