I think it’s a matter of judicious use. I use a lot of tamari/soy sauce when I cook, but not enough that the food tastes overly of it. It’s the savoriness I want, not the actual flavor. Same with tomato paste - roast it in the oven so it has some color and then mix it in with things like soups. They won’t taste like tomato paste (unless you go overboard with it) but they will have a fuller mouthfeel and feel more satisfying.
When I make stock at home from vegetable trimmings, I put mushrooms and kombu in. In Japanese cooking those two things make a dashi, which is a base stock for a lot of dishes, but even adding them to regular stocks (or if I’m cooking rice or quinoa or something) by tying a sheet of seaweed around some mushrooms and then pulling it out when the cooking is done, it imparts a lot of glutamate but not an overly seaweed-y flavor. I don’t eat the seaweed or the mushrooms usually (dried shiitakes have a texture I don’t like), I use them only to infuse things.
Improving cultivation of more types of mushroom would do a lot.
The range of tastes in mushrooms varies a lot more than most people realise - it drives me crazy how many English words are used for the same mushroom (portobello, white, brown, chestnut, crimini, champignon all refer to agaricus bisporus), and how few mushroom varieties most people have tasted.
Especially as A.bisporus is one of the most boring mushrooms in existence.
