Man, if they opened up script submissions, they’d probably be able to reap a LOT of fanfic-grown talent out there. Yeah, the slush pile would SUCK because it’s much easier to submit online than in the days of snail mail and paper, but we’ve had about 20 years of really explosive writing growth with the advent of fanfic online and as far as I know nobody’s really “mentoring” those people in this day and age.
I know people laugh and snort at fanfic, but writing is writing is writing . You’d do as well to laugh at painters who sketch bowls of fruit or sketch nudes from live subjects (as if people haven’t drawn those things for literal centuries!). It doesn’t really matter WHERE you practice and learn so long as you do it, and if fanfic/fanart/whatever gets you going, that’s how you’re going to grow your talent, by practicing over and over.
And some people get really damn good at it. If Trek opened up script submissions again, it’d open the doors to a new generation of writers kicking their careers off.