Lol she's always been better than other shinobi.... Obviously she's never the weakest, but also never the strongest. Unless you are referring to characters wish to bash in a subtle tone.
Sakura is largely hated for her attitude, her lack of contribution to the overall plot despite being a main character, and bandwagoners who find it funny.
Her part I personality was weak, and at some times (Kage Summit) her part II personality would falter, but overall it has improved. Additionally, most people can't respect the role of medics, and so she's deemed mostly useless part II, and bandwagons/trolls are just what they are.
It is virtually impossible to stop her from being hated. Just appreciate the characters for their roles, knowing some will be mistreated. Sadly... That is life on NB.