Have you tested the public beta? Workstation Pro Tech Preview
One of the release notes is this:
New GTK+ 3 based UI for Linux - VMware Workstation Tech Preview 2017 has been
completely rewritten using GTK+ 3 UI for Linux hosts. This not only improves the UI
experience, but also ensures continued support on new Linux distros.
Frankly I don't mean if it will use the system theme, but it should at least integrate better.