I guess Jagya is being mostly critiqued precisely because the way he handled his relationship with Anandi, not because why he left Anandi in the first place. I don't know about others, but I can speak for myself.
1. I don't think I would have hated Jagya if he declared his incompatibility with Anandi right in the beginning (I mean after going to Mumbai) and ended his marriage before entering in a relationship with Gauri. I don't think I would have hated Jagya if he confessed to Anandi in the beginning about his feeling for Gauri and wanted to be released from his marriage. Yes, the family members and the villagers would have been still upset but Anandi would have understood Jagya's intentions clearly and perhaps would have taken the initiative of ending the marriage herself. Yes, I do think dumping your spouse on the pretext of falling for a smarter modern woman is disgusting, but still if you do fall for such a one, then go ahead and end things with your wife first.
2.The point is not that you have to stick with your spouse even if you don't love her-------maybe some people do believe in the sanctity of marriage--------but I am sure most of us understand that not all marriages are successful. However, what I detest is extramarital affair and cheating. If you want to move away from your wife, do it and then start a new relationship. But if you start a new affair without breaking off with your wife first, that's called cheating. Thus people who are bashing Jagya are mostly bashing him for the cheating he did on Anandi, not because he broke his child marriage. We cannot assume Jagya's innocence and excuse him only for his child marriage victimhood, while overlooking all the other things he did as an adult. Jagya comes as a whole package, where infidelity is also included, and when he is bashed, he is bashed for all his actions. You cannot take some issues and overlook others in him.
3. About Gauri I can only say she is in denial. There has been numerous instances where Jagya's faults have been exposed to Gauri----------J as a cheater, J as someone who romanced his wife and then dumped her, J as someone who doesn't respect his family, J as the breaker of family's trust, J as a pathological liar, J as someone who cannot defend his wife, J as someone who still has a soft corner for his ex wife and goes to meet her at night--------------all these flaws are major flaws and for any other girl they would have been enough to wake her up from illusion of love. I don't think any girl would want to spend her life with such a person, and even if she is in love, her love will suffer major setbacks. However, Gauri is a different case altogether. Marrying J has become her obsession and she will not go back at any cost. No matter what J does, how low he falls, Gauri will keep clinging to him for leaving him means she was mistaken and Gauri is a girl with so much ego that it is difficult for her to admit any mistake. So she will burn in jealousy and constantly be pained by Jagya's actions, but she will be in denial and will never confront Jagya lest the object of her obsession leaves her.
That's precisely why she is blind to everybody else trying to drive sense in her---Bhairon, Phuli, Sumitra. Yes their words hurt Gauri and made her doubt her own decision but her ego quickly takes over and she refuses to rationalize on them anymore. That's precisely why she refuses to understand why Bhago is angry and is shouting at her instead. She doesn't want anybody to ruin the illusory image of Jagat she has in her mind. The Jagya she has known in the haveli is constantly breaking that image along with all the other people who are out there to smear her Jagat, and she is desperate to save the last remnants of that illusion. She prefers that illusion over reality and she will live in illusion.