I didn't start liking Laurel until end of S2. But met a lot of posters elsewhere who are big Laurel fans b/c as they explained they followed BC comics and when they heard about Arrow, including how the EPs were selling Laurel as the future BC in pre-publicity, they were excited about getting a live action version of BC. Just like GA fans were excited about getting live action GA. I think being drawn in b/c of a potential BC was just as valid reason for starting in watching the show, as for GA. And I don't think these fans were imagining something -- the EPs definitely implied this.
True, the EPs could have chosen to have a GA story without BC, in which case they could have come up with totally different love interest, starting from scratch. And no need to name the character Dinah Laurel Lance BTW.
Clearly, they botched a lot about the Laurel turning into BC storyline, due to poor writing (starting with the whole sister swapping issue) -- which should be no surprise really in hindsight considering all the other poor decisions they've made with writing etc. The pivot to Felicity, to "correct" their missteps in the romance dept, IMO has led to some major problems -- such as Diggle being stripped of much of his original role and purpose (to encourage Oliver and act as light to his dark), which was given to Felicity, and then also Diggle being turned into a major Olicity shipper and Felicity shiller. Of course, Felicity is not the only problem with this show and Felicity is not the cause of lousy fight choreography. I do suspect the need to start propping up the Felicity character, giving her a backstory and putting more focus on her however has impacted character development and story arcs for other characters. Which is unfortunate as those other characters (Quentin, Laurel, Diggle, Thea ) are directly involved in fighting as well as being in law and police, whereas Felicity in her IT role simply doesn't have as much to contribute to the vigilante/law and order aspect, nor have they made any effort into strengthening her role as CEO which could have potentially served to link the team back into the corrupt businessmen against the little guy storylines.
It's not as clear to me how much focusing on Olicity has impacted giving the villains appropriate focus... another problem with this show IMO. If they are spending time showing Olicity angst which could have been better spent showing Darhk motivations and machinations, then that is a problem...
At any rate, given the path the EPs started with -- Dinah Laurel Lance -- and given that quite a few people do seem to feel that by S3, after character arcs that either were good or not (according to who you talk to ), Laurel did seem to be on track as BC, so it's very understandable that there is a lot of frustration if she does not continue with her journey on this show after this season and frustrating that she hasn't been featured more as ADA/BC story arcs this season. Such arcs would not have to compete with the main story, GA, but could easily intersect with and compliment GA's story. Much as Foggy and Karen's stories intersected with Matt's in DD S1.