I got many replies that quoted parables and similies, such as "The burning house" and "the raft"
It was me who mentioned those two parables, about "the burning house" and "the raft".
Because I am not a guru I wouldn't want to answer a question which asks about Buddhist doctrine (a.k.a. "dhamma preaching") by quoting myself: instead I want to answer by quoting a Buddhist guru (and in my case, preferably by quoting doctrine attributed to the historical Buddha).
It's a mistake to equate my answers with the answers of "modern-day gurus".
Another reason why I quote or reference existing text is so that you can read more of it (more of whatever I referenced) if you want to. For example I linked to Wikipedia's article about Upaya because I thought, based on your question, that was a subject that would interest you.
It's also a mistake to conflate my answers with the answers from other users of this site. For example another user might have chosen to answer your question with a definite "yes", saying that there are several kinds of Yāna for different people.
And (I don't know why) most of the site's users chose not to answer your question, nor to upvote any of the answers.
I find this tendency to stick with outdated imagery somewhat disturbing, because it suggests a lack of original thought-process
Sorry about that.
being able to impart those teachings convincingly in an age-appropriate and context-specific way
You're probably right; I don't know how old you are or how much you know about Buddhism already.
In one of your comments you wrote, "my philosophy is informed by Hinduism", and this was your first question on the site; so I tried to be conservative in my answer, i.e. ensure that my answer mentioned some of the most essential/central Buddhist doctrines.
And actually I'm not trying to be "convincing": instead I'm trying to be "authentic".
I remember this from Confucius' Analects,
Tzu-lu made Tzu-kao the prefect of Pi. The Master said, 'He is ruining another man's son.'1
Tzu-lu replied, 'His job will be to lead the common people and the officers, and to honour the altars to the spirits of the earth and grain. In order to be considered learned, is it necessary for him to study the books?'
The Master said, 'It is for this reason that I dislike men who are plausible.'
because Tzu-kao had a lot of talent but he hadn't yet studied.
(Apparently Confucius was a fan of having studied and being learned.)
So if I write an answer on this site, I try to write something that is true, not just plausible or convincing.
Elsewhere there are many other people's attempts to render the intent of Buddhism or their understanding of Buddhism in accessible, modern language. If you compare http://fakebuddhaquotes.com/ with http://www.realbuddhaquotes.com/ you might (I don't know) prefer the more authentic quotes.
Buddhism is NOT about being able being able to sound like a reincarnated Indian or Chinese sage, or like his favourite student.
I think there are several schools of Buddhism. One is Theravada which is somewhat defined by (and which studies) the Pali scriptures.
There are also other schools (Zen for example) which has a literature of its own, such as this or this.
And there are living people who can try to answer your questions, some of whom will do better than others.
stuck with showing how thoroughly they have read the ancient Buddhist scriptures, rather than how deeply they have imbibed the teachings
I was trying to do neither: I was trying to answer your question.
Maybe next time you could be more specific (in your question) about what you're looking for (in an answer), e.g. "please don't quote scripture". A problem though with trying to do that here might be that asking, "What do you think?" is usually treated as off-topic on this site: because if there are 100 users reading the site then asking "What do you think?" might result in 100 different answers, which isn't exactly the purpose of this site. The purpose of this site is to answer questions; a question which invites an infinite number of answers is, in some sense, a question which cannot be answered (it has no single answer, no single answer is sufficient, it is unanswerable). So instead of "What do you think about X?" you're encouraged to ask more impersonal questions like "What does Buddhism say about X?" or "What is a solution to my problem with X?". In turn, impersonal questions like "What does Buddhism say about X?" encourages people to reference Buddhist literature.
One more thing is that Buddhism doesn't always respond to "yes or no" questions. So if you ask "Can there be one Dharma for all stages?" a Buddhist answer might be "yes and no" (or, the answer might be a criticism of the question). I wonder whether the "wholesome roots" might be a good answer if you are looking for a-single-dhamma-to-suit-all-occasions.