That is because you are, and always have been, overly emotional with City football players and especially Aguero.
I used it to be the same until I met them in a social setting. They’re just people with jobs. Aguero wanted to stay longer for several reasons, he’s settled, he likes the money at City, he likes the club and we are the best ticket to trophies available to him. City didn’t want to offer him a longer term contract and didn’t want to pay him what he’s currently on (which is what he was offered when banging in 30 goals a season at his peak). Aguero didn’t want the offer on the table, he chose not to take it. No one hates anyone else.
Don’t take the whole thing quite so personally. Stop trying to apportion blame. Pep cares about literally one thing, winning matches. If Aguero was doing anything in training to suggest he deserved more minutes on the pitch, then he would be playing more.
Do yourself a favour and unwatch the thread for a few days until you’re less emotionally raw about the situation.