In this post I said I'd comment on 99Seats' post about MTC when I had some time... so here goes:
Basically... it's important to consider the nature of institutions in general when talking about this. One of the key aspects of an institution is that in becoming an institution one of the thing that happens is that its mission shifts from whatever its original mission was to a new one: perpetuating and growing itself.
To take a rather left-field example, the Institution of Marriage has grown beyond its initial mission (the exchange of property and sealing of familial alliances) to embrace all sorts of relatively new romantic meanings as a way of perpetuating itself. This is one of the reasons why gay marriage advocates will ultimately be triumphant, because the alternative-- creating a civil alternative to marriage-- would weaken the institution and threaten its ongoing viability. If you need any evidence, look at European countries where a civil alternative to marriage exists. (If you care, I happen to think this would be a good thing and that the Government should only recognize civil unions and then private citizens and their secular or religious organizations can do whatever they want).
Anyway, back to MTC... what is true for large institutions like "Marriage" and "The Family" (or "the Democratic Party", to take a problematic institution I am personally fond of) is also true of Institutional Non-Profit Organizations. This is one of the reasons why employees of non-profits frequently end up very frustrated in their positions. Frequently they'll be tasked with helping to change the institution in some key way, but the institutional conservatism constantly thwarts them no matter what various individuals within the institution might want.
One force that frequently conservatises institutional theaters are their existing audiences. Time and again as I've sat on panels and had conversations with people and read articles articulating the institutional perspective, they say "Look, we tried everything we could to attract younger/edgier audiences. They didn't come, it doesn't work, we're going back to doing what we're doing." What this generally usually means is: "We adjusted our marketing language to try to trick them into liking the same stuff we always did and we lowered our ticket prices and they didn't respond". The reason why is if they made the actual programming choices that would be necessary to attract the different audience they claim they want, they'd piss off their existing base.
This isn't just irrational fear. I know of several theaters that have tried to take some risks about what material they've chosen in an effort to reach out to new audiences and have taken a bath. They usually respond the next year with even-more-conservative-than-usual seasons. It's a tough nut to crack.
One of the components of this conservatism is what I call the Institutional Racism Hangover. Which is, simply put, the ways that institutional conservatism perpetuates institutional racism. So, as 99 says, one of the reasons why Ruined was considered a greater risk that Accent on Youth is that it didn't have any celebrities in it...but another reason is almost certainly that it's about Black people (I would argue another reason it was probably considered a risk is that it's about women and about rape).
Institutional Racism in American Theater (particularly in casting) is a problem, and it's one we need to deal with. I just think it's also worth looking at the roots of the issue, as they also cut into several other problems as well.
PS: For all of you fans of The Wire, this is one of the reasons why the show was so brilliant, because David Simon viewed it as a Greek Tragedy where the Greek Gods were Civic Institutions. He wanted to resist the modern notion that the individual in society has a great deal of agency. The Wire is, in fact, one of the most honest analyses of our Modern Institutional Existence that I can think of.