Are you qualified?

I've become very aware of the dangers of putting your creative side out there and opening yourself up to criticism. Hell, it's the major thing that held me back after some savaging as a kid in high school and college, and it's taken quite a bit of effort to get past it...and as a consequence I've become very reluctant to throw random critiques out toward people who work in creative fields.
<rant>This, of course, does not include those people who try to succeed in fields that require talent who do not have it. Like, say the usual screeching singers weeded out in the early going on American Idol, or the 'writer' who has yet to finish a novel/screenplay/play/short story/dirty limerick. I've accepted the fact that I won't be playing in the NHL in my lifetime; you need to get over the idea that people can really do anything 'if they just put their mind to it'. Sometimes dreams don't happen for a reason. </rant>
I also know enough that, when it comes to critiquing fellow screenwriters, nine times out of ten what's on the big screen (should a writer be lucky enough to have their work show up there) is not 100% theirs, unless they fund the thing themselves. And since we're talking about writers, that doesn't happen...except for George Lucas...and that's just a completely different conversation.
I also know that writing gigs can be hard to come by, and that, having maybe sold a script, or done some re-write work, and then hitting a dry spell, you need to put food on the table. And this need can lead to some writers offering their services as script doctors, offering their experience to fledglings who need guidance.
Some of these guys (like the dearly departed Blake Snyder, and back in the day Rossio & Elliott) truly mean well and want to help unknowns with talent break through.
But.....
......okay, so if you're listed as the writer of what is widely considered to be the worst film made of the decade (the 00s), one of the worst films ever made, a colossal box office disaster, and it's your only listed writing credit....is that really the guy to listen to?
Sure, maybe they have some good advice about navigating through the minefield of Hollywood for screenwriters.....but I'd think long and hard about paying said person to teach me about building drama when they penned a flick in which thousands of years in the future F-15s tucked away in a bunker without maintenance can still fly on fuel that somehow hasn't evaporated/gone bad by primitive people after spending a few hours working a flight simulator.
Oh, did I give away the movie without naming it? Whooooops.
