Isekai / reincarnation / fantasy mangas have been huge these past couple of years. There are many interesting mangas with various topics and themes out there, but “cooking” is one theme that I can’t get behind.
I love cooking mangas in general. I’ve read Mister Ajikko, Chuuka Ichiban, Yakitate Japan, Shota no Sushi, Oh! My Konbu, Shokugeki no Soma, and many more. In these mangas, no matter how ridiculous it gets, it is usually based on real world ingredients. The final product is often exaggerated but the flavor is something I can actually imagine. I’ve actually attempted to make some of them and read about others who have done the same.
But this is often untrue for cooking scenes in fantasy mangas. For example, cooking is a major part of Drifting Dragons. They would make dragon meat dishes that are similar to real world dishes and go into details about how it tastes. In Campfire Cooking in Another World with My Absurd Skill, Mukoda would make real-world dishes but isekai monster meat, and how great they taste. But… so what? No matter how much you describe the taste to me, I don’t know and will never know how a dragon or orc taste.
I’m not saying those mangas are boring. I actually really enjoy both Drifting Dragons and Campfire Cooking, but I just can’t get into the food part of it. I would probably enjoy them even more if they glossed over the food and spend more time on other things.
I feel like the reason why plenty isekai series add cooking is simply because it's relatable to a lot of people, so it's a decent filler. There are some cases where the manga revolves around food, but even if they'll never taste dragon meat or similar, well, the author won't either! So you're free to interpret it as you like. And readers can still try the recipes out, using RL ingredients, just to get a feel. (That's what I did with banbanji, from Campfire Cooking. I definitively didn't use rock bird, just some plain chicken.)
Then there are cases like Cooking with Wild Game, where the food itself doesn't matter that much; what matters is how the characters use it to relate to each other. Like Asuta and Ai doing swapping the gender roles of the forest people, as she hunts and he cooks. Or how his cooking is lifting up the forest people, things like this.
I strongly dislike cooking fillers in isekai mangas lol. I can’t think of any examples off the top of my head, but it’s typically when the group camps out while traveling to a new town. The protagonist would make some modern dish with isekai ingredients and blow everyone elses’ minds. It’s an overused troupe that rarely adds anything of value to the story. There are other isekai troupes that I’m tired of (e.g. pages of random skills) but cooking fillers is a pretty bad and frequent offender.
Isekai Meikyuu de Harem Wo has a good example of cooking filler. All that Michio prepares is fantasy equivalents of RL dishes, just so the girls say "sugoi" and "oishiiiii". And it goes as you say, it doesn't add to the story.
I hear ya on the other overused tropes. Kumo Desu Ga is perhaps the only one that I've seen that actually uses the "pages of random skills" shtick for anything interesting (in the fight against Araba, to show that both were overpowered monsters - you aren't really supposed to read the full pages for either Araba or Kumo, I think).
And since we're speaking about overused tropes: 90% of the romance tropes in isekai (actually manga in general) feel overused and stale. Like:
For me it's the biggest offender, because I love well-made romance. At least Cooking with Wild Game is handling this decently enough - it's a slow burner but you do see some progress between Asuta and Ai.