Well there are a lot of reasons why people dislike sakura and it happens to be A LOT of naruto fans so I think the fact just has to be accepted that many people do not like her character and leave it at that.
So because lot of fans think that, it has to be accepted? Why?
And what are those reasons?
1) Sakura is a useless fighter -> false, she's among the top K11 and none other of the K11 is hated for being weaker than, say, Kakashi or Darui
2) Sakura manipulates Naruto/is mean to Naruto -> false, she repeadetly shows that she cares about him and that she feels guilty for the promise they made.
3) Sakura idolizes Sasuke -> false, she gives up on him sooner than Naruto does.
4) Naruto is going to be with Hinata -> I certainly hope so, but then again why does this imply that Sakura is crap? No answer.
5) she's frail and her will wavers, she can't always carry out what she wants to -> then why do we all (well, most of us) love Hinata? Is somehow a Hinata-specific right to be frail?
So you get: a lot of statements clearly contradicted by the manga, and one motive that basically signifies "If Sakura isn't Naruto's woman she's crap".
Free to think that. Just doesn't seem all that legit to me.