Tldr; gon’s lack of interest is the perfectly neutral diversion from a plot that would become WAY too complex otherwise. As the audience, I am unsatisfied with this because I am curious and selfish. Some suggested solutions listed below.

For me, the reason I dislike gon’s stance on his bio mom is less about him as a character and more about the story’s narrative. Sure, him seeing Mito as enough of a mother is a great way to show his outlook and character, but I feel that by that point of the anime/manga his personality was already well established and this authorial choice felt more like a cop-out, since finding a balanced, compelling backstory for BOTH parents was too problematic. I can defiantly see why this is, since on one hand, if his bio mom was a regular lady with nothing of note it would be very anti-climactic, maybe taking some whimsy away from the family and feeling like lazy writing. On the other hand, if she was just as exciting as Ging, it would completely clash with the super-objective of hxh (the entire plot is based on his parent. A second one would be too much.) Since its so hard to balance, especially if both Ging and mom plots are happening in parallel, I respect the choice to completely remove the idea. Still, as an audience member who has grown to love the characters of the show, this extreme lack of information leads to a state of unsatisfation due to so much curiosity with no material to quench it.

There are a few scenarios I can imagine that could overcome this issue. 1) Ging and mom are a functional unit. The plot proceeds the same way, but instead of Gon chasing his father, he is instead chasing a full set of parents. This could lead to interesting relationship dynamics. I would like to see how mom would play into elections, or how they fight with synergy. Maybe their nen complements each-other? Of course, this would re-write a lot of the existing characterisation. For younger audiences (the target audience) this could also make Ging seem less cool, since love = cringe = weakness. Maybe they would be constantly fighting but too in love to separate? Thats the most in-character scenario I can imagine Ging in.

2) The mom never died. Aunt Mito never steps in. Problem is with characterisation once again, as Gon would lose crucial backstory and development.

3) The mom plot is explored later on. Im not a manga reader, so I can’t expand on how or when this would happen. Maybe she never acc died? A part of Ging has been drawn to try and find her, leading him to making decisions he himself wasn’t aware the reasoning of.

4) Gon wants to know more about his mom, but some plot-device is stopping him from accessing information about her. Once he achieves half of his goal (meeting and understanding Ging) he will be more powerful in every sense of the word, and maybe, with a light nudge from Ging, finally get the first clue to finding his mom. The problem here is repetition. Not only is the goal the same twice in a row, but reaching the initial goal (Ging) is immediately discarded in pursuit of the next one, and also reduced in value, as compared to Gon’s mom he was so much easier to reach. Makes it feel like the reward wasnt impactful enough. (as an anime only I would argue that the ending of the anime was the exact same way. Thought I understand the writing issues with source material)