Yes, SOME of the trees. You don’t think there are shit trees in Japan? Do I dare say the majority of all trees in Japan? No matter what country you’re in, most of the trees in any amateur practitioners garden are not going to be show material. The amount of high level trees anywhere is just a general factor of the number of people practicing the art/hobby/pasttime/vocation.
The new(er) generation of practitioners here are definitely keeping pace.
@Eric Schrader is producing very high quality JBP in very short time. These trees aren’t going to take X number of years either. I have no doubt many of his trees will go on to be great trees. He’s not the only one either.
Age is absolutely an important factor. Any two trees with similar treatment and care, the older will almost always have more character. It is important enough that we find every way possible to fake it.
In summary, the “DIY mindset” is not holding anyone back. There are those with that mindset everywhere. There are plenty of valid issues that have “held back” US bonsai (access to material, knowledge of indigenous species, etc) but I don’t think wanting to take your own road has been an overall detriment.
Finally it’s worth noting that both high level US and Japanese practitioners have stated that some of the best trees have been found in the back yards of hobbyists.