No, I don't feel preached to at all by having diversity just exist or mentioning as it pertains to the story - that's actually my whole point - I have a problem with it existing and being lauded for its own sake which is very much what the M&M (or just M in this case) do. And in my opinion, I think diversity stops being special when you just keep harping on how special it is without really showing it being special. I guess it just boils down to "show, don't tell" for me.
I'm not glad-handing when I say your Titan novels are the best of the bunch for exactly the reasons you mention. The diversity is just there and when you do explore a race like the Jellyfish hunters from Orion's Hounds (the name escapes me right now) you don't just paint in a broad brush and make them all evil hunter-killers. You also tend to focus in a bit better than most of the other writers of the series. You don't seem to feel the need to just include everyone because you need to make sure you give every race face time. Because of your focus on them, I think Ree and Lavena are two of the more interesting or at the very least memorable characters from the series.