Not quite true. Lots of Thai dishes use a tonne of fish sauce and even shrimp paste in their dishes. They even make side dish dipping sauce (Nam Jim Jaew) that's like basically 50% fish sauce.

No, people have different sensitivity to it. Many people experience Vietnamese fish sauce as a strong “rancid fish” character that is not at all subtle in all traditional recipes that use it. It isn’t “using too much”, it is “using any at all”.

I imagine it is like the people who are sensitive to cilantro, thinking it tastes like soap.

Except the cilantro thing seems to be genetic; disliking fish sauce is simply preference.

I've used fish sauce as an alternative to anchovy paste for caeser salad dressing which is heavily defined by a fishy taste.

I don't think your idea of 'fishy taste' is the same as theirs.

Some people are just more sensitive to certain smells and flavors than others, especially if they didn't have previous exposure to them.

I could not taste the fishy taste myself but my partner can. It varies by person how sensitive they are.

Right? It's there to add a layer of depth and savoury umami

Lots of people are super sensitive to the “fishiness” of fish sauce. I can taste it with just a few drops in a large dish. I love it now, but it took a while to get used to

I think in many dishes you can add quite a lot, but it blends and cooks in with other ingredients so that the "fish sauce flavor" does not jump out as such.

I make mapo tofu with 1 tsp each of fish sauce, oyster sauce and light soy sauce. I don't think anyone would think it tastes like fish or oyster sauce in any way, but it doesn't taste right at all without them. The same goes for many other dishes.

I need to try this. Typically I make my mapo tofu with dry-fried mushrooms and mushroom stock (I've found this much tastier than a pork or beef-based mapo tofu), but I don't always have the mushroom preparation on hand and punching up a pork mapo tofu with fish sauce would be much more convenient.

What kind of fish sauce do you use?

Red Boat fish sauce, Lee Kum Kee Oyster Sauce, and Pearl River Bridge light soy sauce - all standard stuff. I use just a little ground pork for that flavor, and I’ve found a little chicken stock and dash of white pepper really help as well

It's just that it smells absolutely horrible, and so you should be using the tiniest amount possible unless you know what you're doing. The fish sauce is just a cultural equivalent of soy sauce in some of SEA countries, they use it liberally over there. It does taste substantially better than the soy kind if you can bear with the odor(which I personally can't).