There was nothing wrong with his strike rate last year, all he needs is more time on the pitch, plus with players like Nolito, Sterling and Sane wide in a front 3 we aren't going to be overly reliant on the no 9 constantly scoring. Plus, same logic as with any other position, you aren't going to get players at a decent age and good enough to play for us who are happy to be third choice for one position when they could easily go to a club one tier down and start most games. Maybe we could get a Claudio Pizarro style striker happy enough to pick up a wage to play 5 games a season but that's about it really.
Another point I'd make is that with the strengthening we've done in the roles around the striker this year and with a system that doesn't use a normal no 10, he's not going to get any chances in positions other than Aguero's.