I used to think that it didn’t but then my CSA (local farm) sent me some locally grown celery and the taste was astounding. Much smaller stalks but the flavor was incredible and I realized there is a celery flavor.

Yep. If you've ever tried Old Bay seasoning, it's the dominant flavor in that. Apologies to the state of Maryland, but I find it foul.

Of course you could also just bite into a stalk, you'll taste it.

It does, but I only really noticed it first when using celery salt in my tuna sandwich mix. That's probably the easiest way to spot it that I can think. Make a can of tuna and add a lil celery salt and you're like halfway to a proper tuna salad taste just with that alone.

I mean, the reason is that it’s one of the main ingredients of mirepoix, and most people don’t find it offensive. It’s one of those background flavors that you don’t pick out, but is part of the typical base.

What I’m getting at is that if you don’t like it, just don’t use it. It’s there because whoever made it, decided to put it in.

Now, I’m sure there are all kinds of explanations about the enzymes, and the fiber and so on, but it’s soup, doesn’t have to be complicated. Just delicious :)

In addition to what the others said about mirepoix, or stock, soups are experienced as more full-bodied or wholehearted when celery root is added. The earthy, bitter taste can be balanced by the right combination of sweetness (from other vegetables) and saltiness or used as intensifying effect for a strong umami taste, e.g. in poultry stock.

I haven't met anyone who specifically disliked the taste of celery root in soups yet.

Out of curiosity, do you also dislike other earthy tastes, like truffles, lamb, champignons, girolles?

It is a basic ingredient in mirepoix, which is used as a base for a variety of sauces, soups, gravies, and stews. It's just one component of what is basically just a fresh vegetable mix. You can always just substitute whatever you have on hand or local that fits, just like you would with a stir-fry or fried rice. It's less about the specific vegetables than it is about the way they are prepared and what they contribute. Onions and carrots add sweetness. Celery balances those with its saltiness. Celery and garlic feel to me like a bridge to the other proper herbs like parsley and thyme that usually go in the mirepoix I combine with a good roux to make gravy.