I think you have a very good point there, and having looked through a lot of the flameouts, I believe that is in the majority of the cases the reason that people leave. Ironically, in more than one case, I've seen "good faith" get assumed on a troll's behalf while someone who's been around for a long time and generally demonstrated good judgment is interrogated for "biting" them by delivering the ultimatum they should be getting in that case-either stop the problem behavior, go away, or get helped to go away.
To that, I can actually see solutions.
-I've suggested that new users be disabled from creating mainspace pages (mainspace only would be best if it were technically feasible, this would still give them the ability to create their user pages, start up discussion on a talk page if the page hasn't yet been started, etc.) until they've been around for 4 days and made 50 edits (or perhaps 20 mainspace edits.) If someone can manage to make 20 mainspace edits, stick around for 4 days, and not get indef blocked, they're probably not an idiot or a vandal, and they've probably started to gain at least a limited understanding of content policy by working with existing articles. They probably also should be restricted from uploading images during this time. If they want to upload free-use ones, they should be doing that on Commons anyway. If they want to upload fair-use, they shouldn't be doing that first thing upon joining anyway.
Yes, this will deter a few good people from joining. It'll also deter a lot of bad ones, and knock down the neverending CSD backlog. If anything, it's more "bitey" to say "Well, that new page you made about your (best friend/grandfather/loved one that just died/favorite obscure (band|website)) is going to get summarily nuked" rather than "Hey, before you make a new article, we'd like to be sure you understand a little about how things work here. If you're convinced you've got it down already, wait a few days, or articles for creation is right this way." The CSD backlogs and newpage patrol burn out a -lot- of admins and patrollers, and are inordinate timesinks as well. We don't just need to ask ourselves "But what if we miss out on one good article that way?" We also need to ask ourselves "If the number of articles we must speedy is reduced to a quarter its size, what could those who are tagging and deleting them be doing with the time instead? What if we're missing out on thirty good articles that way, as well as a ton of improvements to existing ones, and burning out great editors in the process?"
-There's no reason for vandals to be given 3 or 4 warnings before the hammer comes down. They should get one, telling them their conduct is unacceptable, period, and if they pull it again they get a nice block. If they apologize nicely, and clearly understand why it happened and show intent to quit it, there's always an unblock button. In my experience, however, it's pretty rare that a vandal suddenly "comes around", except in a few cases of test editing where they go to the sandbox instead. Again, the question is "What if half the RC patrol could be dispatched to the cleanup and wikification backlogs instead?"
-We need, as a community, to be a lot quicker to give the boot to trolls, edit warriors, and POV pushers. This goes triple if they're single-purpose. It's very rare that these people "come around", or do anything but drive good people off the project.
-We also need to come down a hell of a lot harder on people trying to own articles, or who are a little too liberal with reverting. Every time you make an edit, you can look right down below, and it'll tell you "If you don't want your writing to be edited mercilessly or redistributed by others, do not submit it." OWNership drives a -lot- of people off, and prevents articles from ever being improved. If at all possible, and there are no overriding concerns (such as BLP or complete factual inaccuracy) which demand immediate reversion, poor but relevant and good-faith edits should be sourced, improved, and integrated, not reverted. And those who revert well-sourced material relevant to an article because they don't like what it says should be shown no mercy whatsoever.
-We need to make cutting easier, and quit calling people who trim down, merge, and delete articles "vandals" or "deletionists". Cutting is a healthy, natural part of the editorial process. (Of course, this presumes that such cuts are made with a clear rationale.) Once again, people need to see that sentence in the edit window. If you don't want your work edited, possibly beyond recognition, possibly even removed, certainly without your approval, you're posting it in the wrong place.
-People who don't discuss a questionable action with the person who took it before heading to ANI or RFC or wherever else need a good troutslapping. Sometimes, the person may really have a good rationale (or bring to your attention something you didn't know), and the matter can be dropped. Other times, you may convince them (or bring to their attention something they didn't even know), and they'll happily reverse themselves. Of course, the same applies to those who refuse to discuss issues with those who do raise civil questions about their actions and explain the rationale behind them, therefore virtually guaranteeing escalation.
My apologies for the length. I do believe if we can solve these issues, we can significantly and realistically reduce burnout of good editors and admins. If we lose a few trolls, vandals, and vanity bios in the process, well, that's just an added bonus.