I've never seen a quince tree, or an azalea tree, and neither have I seen many of the species we use as a bonsai as full grown trees. For a large part that is due to the subjects being shrubs by nature.
If you want a tree, plant one in the yard. If you want a bonsai, then plant one in a pot and make it look like a bonsai, or make it look like a tree, or make it look like a balloon animal.. There is no bonsai police.
It took me a few years to understand the concept, the way of (free)thinking. Bonsai isn't just copying what we see in nature, sometimes it's enhancing features we see in nature, sometimes it's dulling down features we see in nature.
Walter Palls naturalistic style trees for instance, aren't naturalistic in my area; we only have telephone pole pines, our beeches aren't hollow and if they are they usually die within a few years, our oaks don't live past the age of 150 years in the woods because they'll succumb to either insects or fungi or the weather. Even our junipers are straight as an arrow, usually with one giant conical bushy canopy up top. I still would prefer mine to look like the ones posted by Adair.
Why?
Because in my case it's what I like to look at. Don't get me wrong, I used to think all junipers looked too worked, too fake, too stylized. The whitewashed deadwood and sometimes even painted live vain were enough to make me barf in my mouth.
Then I gave junipers a go, they're versatile, they can take a beating, they can be made into almost anything we imagine. That's pretty radical, and not a lot of species have those possibilities. Let alone that it looks convincing, and honestly, sometimes it doesn't look very convincing at all.
I feel confident saying that most bonsai don't look like miniature trees. They just don't. If you would upscale them as they are, they would look like enormous trees, with leafs the size of a full grown person and flowers the size of a car. Now, does that bother me? Not at all. It also doesn't stop me from appreciating bonsai, or miniature representations of full grown trees, or the full grown trees themselves. But it's a mental hurdle to overcome nonetheless.
Thought experiment:
Shetland ponys are horses, but if you'd genetically alter them to become as tall as a regular horse, they'd look pretty awful.
Imagine a Danish dog sized chihuahua..
Scale down a full grown pine to just the size of a hand, that's 30 meters to around 15cm. Those 5cm needles will be around 0.025cm now. 1/4th of a millimeter in length, and so thin that they'd look like algae if you could even see them.
Scale up a barbie doll to human size. Her eyes would be the size of tennis balls. And trust me, there are a few people that tried to look like a barbie doll. Ask any kid and they'll tell you the doll looks better.
Is that scaling really a thing we should do in bonsai? Are we doing it in other art forms or even other things in our society, like toys and horses? How would that be working out if we did?
I don't need anyone to answer those questions, but I think it's good to think about those kind of things every now and then.
A year or two ago, I could have written this thread with the same idea. I just didn't get junipers. Learning how to work junipers and seeing a few prime examples did change my way of thinking about them.