I installed the ARC theme and that has helped a little, but it's still not really good.
sudo dnf install arc-theme
After installing the theme, go to the Tweak tool, under "Appearance | Theme | GTK+", and select Arc-Darker. Now all dialogs in Eclipse are marginaly legible, but not really pretty. There's a real disconnect between the Gnome themes and Eclipse.
I just recently installed Eclipse Neon.1 on Fedora 24 (sudo dnf install eclipse) and find that the default dialog color scheme results in white text on a very light gray background, rendering the dialogs un-readable. Here's an example...
To fix it, I navigated to "Window | Preferences", expanded "General" and clicked on "Appearance". Tweaking a few settings resulted in dialogs that were readable, but then saving the settings and restarting resulted in no change. I finally got a set of settings that works mostly, although the "Eclipse Launcher" still is broken, no matter what settings I choose.
Here are the settings I chose, which mostly work. If you have any tips on how to fix this right, I'm all ears. Please post in the comments section and let me know....