You can't change anything about any UI without getting someone who doesn't like it. By the same rule, not changing it also doesn't make everybody happy.
I'm not the only person in the world that's completely sick of so-called 'modern', 'minimalist', 'Material Design', 'metro', 'human interface', or whatever else they're calling it. There is genuine criticism out there, and also support from others. I'm not telling anyone which one to run. Give the users the choice.
ST3 has apparently decided to completely abandon it and leave it to third-party developers. So be it, as long as their extension API can fully support it.
Luckily, there is choice. E.g.:
THANK YOU, this is exactly what I was looking for, and this is what @wbond and other admins should be recommending to others that ask in the future.
It's apparently a bit broken after the v3 rollout, but they've got a github page, so I'll head over there and file a bug report.