He used to be a goalscorer, but those days are long gone. He's declined so badly and lost a lot of his pace. He's had a lot of injuries in the last 18 months.
Yeah, he'll be a free agent, but he's going to demand a big signing-on fee and big wages. It's a risky signing for an injury-prone 33-year-old player. There is no way we just offer him a 1-year deal... he'll be getting at least 2 or 3-year deal. Also, there's a reason why City is so quick to let him go. He's nothing more than a backup player now.
My point is that it's instantly seen only as a ploy to keep Messi and all of those other things are overlooked. Even the staunchest Anti-Messi members, (bbz is typing) has to admit there's more than one reason to sign a player of Aguero's caliber.