Different tastebuds can be a dealbreaker. Because food is very important and also a big part of some cultures. Imagine marrying someone who is so picky he can't eat vegetables or someone who puts ketchup and ranch on everything. Now the wife loves food and cooking, she and Jiho were coworkers. Spending a lifetime with someone you can't even share something you love with must be very heartbreaking. She deserves to enjoy what she likes too and Inwoo was just not the right person for her.
Yeah you explained it! That’s why inwoo said they were both immature. It wasn’t the tastebuds that was just the outside layer of the issue it’s what you noted and the main reason was shown when she said she didn’t want to be unhappy like him and was struggling because of him. Mainly it was inwoo’s deep trauma of abandonment wounds from his mom and having a father who wanted to kill him / died and he wasn’t able to process these wounds and probably didn’t open up enough to her to communicate this and she felt the distance and didn’t feel happy with him as he was always unhappy. Or maybe he did share with her and it was too much. They were young and struggling, maybe if they met later in would have worked out, or maybe it was never meant to be

This is interesting but I can’t help but think the reason why the wife and him split up was dumb. If that’s the only reason they both have literal issues idk how they function in society. Or rather how they even got together. Maybe I lack common sense and this is a big deal idk