Things have gotten *somewhat* better the past few years. One strategy I use that helps a lot is to start conversations away (in time and place) from sexytime. Usually while we're chatting on the living room couch (which is off limits for play because it's right in front of a window facing the street). I think if it's clear that I'm not seeking sex right *now*, and that this is just a conversation, it releases some of the stress and she feels more comfortable engaging.
Another well-known strategy that I've gotten better at employing: use "I" words, not "you" words. "I feel X ....", "I would really enjoy experiencing ...", "I know it's inside my head, but I feel neglected lately because ..." Less threatening, doesn't shift the burden.
And finally, we've started an indirect strategy that she seems very comfortable with. She's a big reader, and belongs to a book club. So we started our own. On Sunday mornings, we start our play time (after I feed her breakfast in bed) with me giving her a foot massage ... typically for 90 minutes (I'm a service sub

Of course, I think it might also help that I'm caged 24/7 for the past four years, and she has learned that she's in control ... so that even if I bring up a sex topic (whether or no I was trying to lead to sex), she doesn't need to engage if she doesn't want to.
Not saying that it's all roses -- she still doesn't initiate sex conversations, and still is less comfortable during them than I am. But we've made a lot of progress.