Oof. I use my usuba regularly. I even have two.
There are plenty of folks in Japan who use an usuba for more than just katsuramuki or making kaiseki or shojin ryori. For people who grew up using Japanese single bevels, they’re very useful and not single purpose or gimmicky at all.It’s also a generational thing I think. Most of the grannies I grew up had either an usuba or nakiri along with a small bunka or petty. And that was pretty much it. These days the younger folks usually just have 1 small gyuto or santoku.
But look at it from this perspective: if you have a bunch of foreigners who don’t really cook (and if they do, who don’t cook the kind of food of the knife’s culture) what are you going to sell them? It’s 100% true that a gyuto is more robust and multi-purpose. It’s also 100% true that a gyuto can’t do what an usuba does. There’s also the factor that for the longest time, non-Japanese people didn’t know how to sharpen single bevel knives and use totally different cutting techniques. Of all the single bevels, it’s the easiest to wreck. That’s why the de facto position for so long has been “don’t buy an usuba, it only does a few jobs.” Because for it was almost guaranteed that selling a non-Japanese person an usuba would result in it either being damaged or unused. For the most part, it’s been a self-fulfilling prophecy (as evidenced by your own attitude). I admit, I’ve steered plenty of people away from them using this same logic.
But in his lauded book Japanese Cooking, Shizuo Tsuji lists an usuba as the one knife to buy if you’re going to buy a knife from Japan. That’s because he considers it the one knife that doesn’t have a western equivalent and one that is useful in Japanese cooking (again not just the fancy stuff).
It’s not that the usuba is a gimmick. It’s that it’s designed for Japanese food and cooking techniques. KKF is probably the largest repository of English language info on Japanese knives, sharpening, and techniques, but it seems like less than 1% of the active members on here are Japanese chefs. That’s probably why KKF and by proxy the rest of the knife world got this opinion.