Eh, announce you’re leaving if you’ve got stuff a lot of people use or care about, but leave your feedback in the designated What turns you off playing Boundless? thread.
I say this not to segregate your feedback away from people, but because it is where the developers have asked that the feedback go - so that they have a collected place to see it. The devs are the only ones who can do something useful with your feedback, so leaving it there is the most productive thing to do with it.