My Post-Tonal Analysis professor (who is a composer) went off on a rant about how nobody wants to play new music and how composers don't make a lot of money, particularly in comparison to conductors, and how most composers teach as well as write because of this. I have this to say in response.
The reason that it is possible for people who are not very very famous to make a living off of playing, or conducting, is that they will play(/conduct) anything. Classical, pops concerts, church gigs, pit orchestras. These people are also frequently required to teach, and even more teach regardless of requirement for extra money. This is the way of life. The number of people who live off of only playing pieces that fit into their personal aesthetic is absolutely tiny. Even if you only play in the sort of group (chamber, orchestra, pit, etc) that is your top choice, I guarantee that most musicians have to play quite a few pieces that they don't want to, or at least wouldn't otherwise choose.
So, go ahead and separate "post-classical" conductors from those who (albeit implicitly stated) sell out by doing films/ads/video games. But you have to make the comparison fair.
I understand that with composing the whole point is to create pieces that are music in the vein of your personal aesthetic. And perhaps the world is less kind to Artists of the composer variety than of the performer or conductor variety; the latter two can sort of play on the classical-musicians-as-rock-star-equivalents idea that's hung over in many ways from the 19th century. But honestly? Unless you're a true genius, there's little room for Artists of any sort if you want to get paid for it.
(My opinions about orchestras playing new music are separate and not relevant to this discussion, but I will say that there's a lot more to take into account than "oh, the poor composers who are rejected by everyone".)