I don't agree with your basic premise here.
In other words, rewarding low-quality questions, encouraging the
writing of answers solely for the non-expert, and discouraging
technical answers to technical questions is probably not healthy for
the site. Higher-quality questions and higher-quality answers will
eventually lead to more traffic for the site; isn't that what the Pets
SE community wants?
I'm going to leave the question of low-quality questions aside for a moment, and address the answering part (I suspect that the core visitors of this site spend more time answering than questioning).
I have on multiple occasions written detailed, technical answers to technical questions. I'm not sure how well I'm translating the science language to non-expert, but that is part of my actual, paid job, and I've been told I'm pretty good at it for engineer (for whatever that's worth). Some examples:
You'll note in the comments of these answers no one is chiding me to write for a less technical audience, even though I do discuss some technical stuff (the Whiskas question in particular has some interesting modeling). The key in my writing is that I make sure to explain terms that may be unfamiliar to the lay audience while still using the more technical terms for the majority of my explanation. I think that's the balance that we should strive for.
To address your points in particular:
1. Vague, Unresearched questions.
Yes, we tolerate unresearched questions. We are a beta site and still figuring out what works well in this format. We're establishing the lines for when to close vague medical questions for not enough information, and that is really the low hanging fruit in the "this is really vague" category. We'll get there, but I'm not particularly worried about it because some vague questions don't benefit from extra effort/research.
Also, your linked question is literally from the first days of the site, when folks were just throwing darts at the wall to see what stuck. I wouldn't consider anything from 2013 to be a particularly good example of the culture of this site.
2. No canonical answer possible
While there are not canonical examples for how to train a specific behavior, it does meet the criteria for good subjective.
Let me talk about a situation I'm more familiar with, my answer for "How do I stop my cat from peeing on rugs and linens?" I've had 3 cats not use the litter box. It doesn't matter how much detail someone gives, there is no way to recite the cat's situation and then definitively say "if you change X, she will use the litter box again".
Specifically, it took me 2 years to get Ginger to reliably use the litter box, and that was after the rescue had worked with her original family for months to try to get her to use it again (they eventually decided it must have been the presence of the new baby, but we discovered when she arrived at our house (no kids) that they were wrong).
Ginger's litter box issues illustrates one of the basic principles of working with animals. Unlike computer programs, or cooking recipes, or just about every other subject covered on this site, animals have their own unique personalities and they are not able to verbally communicate their needs to us.
Sometimes we have to lay out 6 trays of different types of litter (did that) to see if the cat has a preference. Sometimes we have to put another dozen boxes in random locations to see if the cat has a preference. Sometimes we have to do literally years of detective work (trying everything you can possibly think of) to figure out what is going on and find the proper setup for the animal.
That work has to be done by the owner, not by someone typing into a text box on the internet. We can give them ideas, but Ginger's particular circumstances stumped a LOT of people (and me for a long time). There's no way people on the internet can think of every possible combination of events to put in their answers, but we try to write as completely as we can, and help each other to add things in when we see places where an answer can be improved.
3. Aiming for Lowest Common Denominator
Unequivocally, I disagree with you here. I spoke above about how I try to balance the technical jargon/language with lay person level explanations of what those ideas mean. I think that's what the moderator comment was aiming for (not write for the lowest common denominator, but provide some context or directions about what/how to train that "bomb proof recall").
It is a balance that we have to be aware of, and it helps for folks to remind each other. When I've been researching an answer for 2 hours I might forget that not everyone knows what strabismus or pica (conditions I've had in my cats), so if I write an answer I might need to be reminded to explain it. We ask for added information in answers to make the answers better and applicable to a wider audience.
4. Expecting answers outside the scope of question
For myself, answering every medical question is an ethical balance. One thing I've learned in the last year of this site is to not underestimate the level of inadequate care that people are willing to subject their pets to. After some of the questions that we've had I feel that I can't assume any level of knowledge on the part of the questioner unless it's someone who has also been around for a while and I have an idea from their questions/answers/chat what their views are.
If I have any concerns about any advice I see on the site, I will point them out because even though I know that cat needs to see the vet, someone's first thought was to post on the internet.
I don't think it's really expecting answers to cover everything, but we're looking out for each other because no one wants an animal to come to harm over something one of us said. That's culture I'm not interested in changing.