One assumption is that code should make sense to anyone who doesn't know the language it's written in. We wouldn't apply that to C, or to English for that matter, so why APL?
Another assumption is that short variable names always make a program more obscure.
Another assumption is that concision makes a program less readable. This assumption runs so deep that it's hard to even see it, but consider: one concise line of code is harder to read than one verbose line, but much easier to read than a million verbose lines. That is, in the time it would take me to understand a million lines of verbose code, I could learn the language of a concise program from scratch, work with its short (and at first obscure) codebase long enough to understand it, and still have orders of magnitude to spare. At some point on the code size curve, the tradeoffs change dramatically.
I don't know the OP's program but I can tell you that the APL culture is a mature, sophisticated, and beautiful approach to programming that occupies a different local optimum than most programmers are used to. To react to this not just with disagreement but outrage ("disgusting"!) is quite interesting. There's something threatening about encountering an approach to one's area of expertise that is so radically different, based on such different assumptions, as to be outright alien. Our reflex is to dismiss it forcefully. But if you can catch yourself doing that and stay with the unfamiliar long enough to get over the "disgust" response, the reward is magical.
A more familiar example to many on HN of the same regrettable response would be the way React was first received. Despite having an interesting approach to solving some common practical problems in web development, and despite the underlying theory being tried and tested in other contexts, some people seemed to reject it just because it didn't maintain a clear separation of HTML, CSS and JS code, which in their minds was a deal-breaker even though there's no objective reason that such a separation is necessary.
Another assumption is that short variable names always make a program more obscure.
Another assumption is that concision makes a program less readable. This assumption runs so deep that it's hard to even see it, but consider: one concise line of code is harder to read than one verbose line, but much easier to read than a million verbose lines. That is, in the time it would take me to understand a million lines of verbose code, I could learn the language of a concise program from scratch, work with its short (and at first obscure) codebase long enough to understand it, and still have orders of magnitude to spare. At some point on the code size curve, the tradeoffs change dramatically.
I don't know the OP's program but I can tell you that the APL culture is a mature, sophisticated, and beautiful approach to programming that occupies a different local optimum than most programmers are used to. To react to this not just with disagreement but outrage ("disgusting"!) is quite interesting. There's something threatening about encountering an approach to one's area of expertise that is so radically different, based on such different assumptions, as to be outright alien. Our reflex is to dismiss it forcefully. But if you can catch yourself doing that and stay with the unfamiliar long enough to get over the "disgust" response, the reward is magical.