That is fair enough if you think they Oliver should have found another way by now, but they have suggested that they are trying to find another way. It is good that they are not ignoring it, like they ignore many other issues (I am still wondering where that runaway missile is going to end up).
Oliver has changed in many ways from previous seasons. In season 3, Oliver believed that the ends justify the means and that you must do what it takes to stop the enemy, especially against a foe as formidable and resourceful as Ra's. Amanda Waller teaching Oliver to torture people to get what he wants, and him doing it to people. Oliver was willing to work with Malcolm so that he could beat Ra's, and even handed him the LOA because he felt that it was worth it. Oliver bringing Thea back with the Lazarus pit, even though he knew that there would be consequences. Oliver joining the LOA because he felt it was the only way to take them down. Oliver killing the LOA member and Ra's al Ghul, because he thought there was no other way to beat the LOA, despite his no-kill rule. Oliver willing to kill himself in a plane-crash, so that he would take Ra's with him. In season 1, he killed people much more freely.
This year, when Sara was out of control and like a wild animal, with others wanting to put her down to put her out of her misery, Oliver found a way to help her, and did not do anything desperate, despite everyone else wanting to. He found a way to save Thea without sacrificing either Malcolm or Nyssa too, despite them both wanting to kill each other and not giving Oliver many options. He trusts his friends more this year, as not doing so last season caused him problems. Darhk offered him the chance to work for him, and he considered taking them down from the inside like he tried to with the LOA, but ultimately decided against it. He is becoming more pro-active by running for mayor to help people different ways and improve the city. He is constantly trying to better himself, despite all of the difficulties that he faces.
He is very different to what he was before, but he is still not perfect. I did not expect him to kill Darhk, and I was hoping that he wouldn't. But after trying to put Darhk in jail backfired and resulted in Laurel's death, I understand him still not knowing what to do in such a situation. His journey is not complete, but he has made progress. I don't trust these writers with much these days, but the fact that they showed Oliver not feeling right about killing Darhk makes me think that they will have him find another way eventually. Fair enough if you think they should have done it by now, but they still want it to be a challenge for him to overcome.