That ending really curveballed any opportunity to discuss things properly but I always like to waffle on these topics. Japanese food is a lot more mild and intimate in flavour profiles. I will say this now that I much prefer spicy food or foods that have some deep level of seasoning like a mixed masala. However, this isn't to say that Japanese food tastes bad to me. It's just a lot more mild in flavour than what I am used to.
I will say that if you haven't had authentic food in Japan then you haven't fully experienced the quality of Japan's food - their fish is especially high quality and any other foreign sushi by comparison feels like a cheap imitation. Unagi or eel meat is among the best due to it being refreshing and filling at the same time - it is expensive in comparison to other fish or meat. The ramen and udon is very hit and miss. I personally find the meat in ramen is underseasoned and has a mushy texture rather than a nice bite, but that is just a small sample of my personal experience. As for "spicy food", Japan is not known for spicy food. Japanese spice tolerance is among the lowest and you might prefer Korean food given that they mess around with chilli spice more.
Now, you're entitled to your opinion, but to flame people for liking Japanese food is a bit weird. I think it's definitely an acquired taste if you're coming from heavily seasoned cuisine. Don't get it twisted because spice is life to me. But sometimes you got to roll back your palate to enjoy some of the intimate flavours of food. Spice tolerance aside, there are flavours you might be missing because you're just searching for some kick from masala or chilli peppers.
Side note, we all lack vitamins in some capacity so it's not even the dig you think it is. I know I take Vitamin D3+K2, C and Zinc supplements and it has helped me quite a bit.