This is my 'genetic lot' versus what I've made out of it. And the 'after picture' is actually a couple years old at this point, I'm thicker now than this.
But I have to admit, I understand your thinking, because I did the same thing early on in my lifting. I felt like I was getting 'wider', and stronger, bigger overall, but just not getting that 3D effect I was looking for. It really sounds like you're approaching it appropriately.
You didn't mention deadlifts or pull ups, which are my 2 main staples in my lifting, along with loaded carries. I think HEAVY loaded carries can effectively translate to a thick back. Most people don't do heavy enough carries to make a substantial impact. I carry frames up to around 450 in training, and more in competition, whereas I know most people who do farmers carries in the gym are working with 80-100 lbs dumbbells. I think you won't really see the results you likely want with less than 150 per side. Once you get into that range it starts to really produce results.
And deadlift heavy. Nothing has improved my back overall more than that.