I don't really get instant miso mix, since making proper miso soup barely takes as long as it does to boil water and return to edible temp, depending on the ingredients you pick.

Be sure to add the ingredients in order of how long they need to cook, typically I'll pick some of the following:

If you add eggplant, carrot, or daikon they have to cook the longest, slice thinly, it has to boil for 8-15 minutes or so before you take it off heat.

Kombu, shiitake, green onions, red cabbage is 3-5 minutes.

For fish, boil the entire fillet for 30 seconds or so, remove, dice, and readd it when it's been taken off heat.

For bonito flakes, Wakame, tofu, 1-2 minutes or so. Typically you want silk tofu.

Finally, add the miso paste once you take it off heat. Stir constantly until the miso is dissolved.

Technically bonito flakes aren't vegan, they can be subbed for mushroom or veggi stock, probably. Maybe some vegan comrade has experience here?

Most of the time I make it I just use daikon, kombu, shiitake, green onions, bonito, tofu, wakame, miso paste. The bonito, tofu, and miso are really the only vital ingredients.