Although we don't really know Gaffur and Zainab's whole story, we can still assume a few things. And in this case I'm assuming Gaffur loved Zainab. From what I understand, Gaffur and Zainab were married secretly and on the other hand, Gaffur's family had arranged his marriage to Razia. First of all, the circumstances because of which Zainab and Gaffurs marriage had to be a secret is not really given. Even so, if he had really loved her, the least he could do is introduce her to his family or just say no to the marriage! Anyways they were already married so what could his family even do? Ok, even if he didnt want to do that, he could have atleast said no to the marriage. This is where he made the biggest mistake of all and where I actually start pitying Razia. Gaffurs had many opportunities to stand up and today he Zainab and Zoya would probably be one happy family. As if that wasn't enough, he knew that Razia killed Zainab and he helped Razia cover up her crime. Why? because he felt 'bad'.
Rashid, even after being trapped in circumstances caused by Razia, could have done a lot of things other than marrying and living with Shireen. He claims that he always loved Dilshaad and yet he stayed away from her, and kept following Razia's orders blindly. If he hasn't been so spineless, today he would be happy with the people he loves the most without regretting these past 18 years of his life.
Yes, life messes up most of our plans but its how you overcome them anyways that really counts. Asad, Rashid, and Gaffur were all separated from their true loves at one point in their lives, but out of all of them only Asad overcame his destiny and claimed his love after facing hardships, something that neither of them could really do. This act shows Asad's love for Zoya and it actually makes me doubt if Rashid ever did love Dilshaad, and if Gaffur ever did love Zainab.
*note: this is clearly all my opinion and if you'd only agree or have something to add, please do it in a nice way. I'm not bashing the characters, just pointing out their flaws.