New Users creating New Articles
The problem could be new users creating new articles, or new articles by new users being deleted. I would not say from the outset that it is the former and not the later. If Wikipedia wants to grow and attract new users it has to accept, that more people will have more diverse interests. If existing users delete everything they personally deem unimportant, then they will remain among themselves.
That would have to be addressed by changing the deletion policies on en.wikipedia — to overhaul them and allow articles that are currently considered non-notable, advertising, spam, neologisms, etc. to be kept. But simply allowing a new editor's article to remain for a longer time, until it were deleted under current policies, would only add to their frustration since they would likely put a great deal more work into it before their project is deleted.
No! The project does not improve by welcoming new editors who write crap so they will continue writing crap. There is already too much advertising (a lot of it well written by corporate PR flacks), spam, and articles about trivia. The goal is to help new editors understand and conform Wikipedia's content standards, which are already much looser than the standards of traditional, professional publishing. A lot of experienced editors treat well meaning newbies badly, with nasty edit summaries on their reverts, nasty talk page posts ("Welcome to Wikipedia, thanks for your contribution, but what you wrote is utter nonsense ..."), and overly aggressive use of warning templates.
I disagree with you about "articles about trivia". One man's trivia is another woman's hobby, and if it meets notability, it's not trivial. Moreover, in some cases it seems to me the notability guidelines are too strict; many academics only meet them once they die, when obituaries become available, even though they are major figures in their fields.
I agree about the rest though.
One question is what is perceived as "nasty edit summaries". I recently observed a non-native english speaker edit warring on english wikipedia about grammatical correction made by a native speaker, who as it happens writes extremely well. I don't remember the edit summary used by the corrector, but it was probably "copy edit" or similar.
Re: edit summaries - when I correct what I think is a grammatical error, I try to link to a Wikipedia article that explains it, such as Dangling modifier from the edit summary. Links are especially necessary in edit summaries with Wikipedia jargon or shortcuts. Unlinked jargon annoyed me when I was a newb, especially after I learned how easy it was to link. I realized there were other editors who couldn't be bothered to make themselves understandable by typing a few extra bracket characters. So I vowed not to make the same mistake too much.