One thing I'm noticing here is that it seems like you are aiming to keep the discussion subjective-analytical with regard to LLMs, while others may actually think this perspective effectively locks out the ability to observe e.g. the face-validity of their arguments which you described. So you have not only "it doesn't understand" but also possibly "it doesn't understand, in a way that you can't see, because if you could see it in that way it'd be obvious, therefore there's no point in continuing the discussion."
This is a common issue that arises in tech communities, where some are willing to sit with the tech and probe it, while others are effectively psychologically locked out of it by default; they spend their time looking at technology as something more pattern- and period-bound, e.g. the technology curve and cultural timeline-positions relative to that curve, relative to a type of product, relative to a single product.
IOW the big-picture scope & associated viewpoints naturally enforce some limits on the tech which are not as easily observed by interrogating / examining / analyzing the tech itself. Those who view life _through those viewpoints_ by default will find it a bit strange that others even have to ask why a thing has the described limits.
This can also be described as a systems-viewpoint on tech, in which individual movements (be that AI w/ LLMs or whatever) are part of a whole and this whole must transact with other wholes. At such a level there is a tractability of the hand-wave that is frustrating to those seeking to understand the broader concepts by examining the item at hand (it doesn't understand? So what does it mean, to understand? Let's discuss its property of understanding), as opposed to the scope in which the item exists (it doesn't understand in the broader sense of X or Y; let's discuss what understanding means in broader terms like the scope of its design, rather than the conversational effect of understanding).
Further, I think it's important to acknowledge that there's sometimes substance behind the "no one owes you a debate" perspective. Especially with regard to a conflict of natural viewpoints on things. If you tend to insist on a debate that is constrained to local limits like "define understanding," and this is in effect too subjective or too local for the other party, then you are essentially asking the parties engaging in debate with you to "think like me", or else justify why they won't do that. So now the problem set has an extra layer of translation-fatigue.
This is an area of interest for me personally, and I see it all the time in communications within tech communities. It can really be frustrating due to some additional, fairly effective/interesting theories about how big-picture thinkers can be perceived as "grandiose" by "I'm just average"-perspective-preferring folks, and so on. So the arguments will even take on an emotional tone due to an implication of impropriety of thought process, so to speak.
Further I'd add that some tech communities are naturally much more _about_ bringing forward the best parts of the technological spirit of the past, and less about celebrating what's just arrived.
Such communities may be more likely to celebrate the 8-bit era, or the migration of a humble form of enterprise-level tech to the home environment than they are to take the higher-dopamine perspectives on how new tech is taking the world by storm. In fact, when the latter arrives, it is greeted with exhaustion. Oftentimes it's less a logical position, especially if you consider that it may not even be conscious to the subject taking the position. So naturally they may not feel comfortable sticking around to debate, but I'd point out that sticking around or not doesn't necessarily have a bearing on the validity of their opinion, though I'm sure it's frustrating to experience sometimes.
Just some thoughts though, it's an interesting q in a lot of ways.