I'm not going to argue that their pre-Adrenaline drivers were very good, but I've found the Adrenaline drivers to be quite well written.
Getting 72% improvement in specific situations isn't necessarily an indicate of something written poorly, it can sometimes just be not getting the time to make some insane optimization work right. For instance, I was just working on this piece of code recently and got it working 100% correctly. It was clean, easy to understand and bug free. I was told to make it faster, so I spent a whole bunch of time to make something that isn't very easy to read, took a long time to get bug free, but performs 60% faster. In this case, it was worth spending the extra time and making it harder to maintain. One of our customers still wants it faster. I know of a couple of way that I can make it a little faster, but it will take days to rework and lots of testing to try my best to make sure there are no possible problems.
A lot of the time, you can make something faster, the question is at what cost? When is getting just a little bit faster not worth the time to squeeze out more performance. When does the risk of something not working properly because you can't think of, less test every possible scenario?
I hate Nvidia drivers! They are buggy spaghetti code. Yes, they are fast, but often at the cost of being buggy. Actually some of the biggest problems in the Radeon drivers has nothing to do with bugs in the Radeon drivers, it has to do with things being optimized to be able to work on Nvidia's crap drives. Sometimes in DirectX 11, or before programmers call non-standard Nvidia only calls without checking to make sure they exist first. This has caused AMD to have to add these non-standard calls to their drivers and map them to standard calls, but until they do so, some of the games don't work properly. Fortunately Vulkan and DirectX 12 have done away with a lot of this.
As for getting Minecraft up to 79% faster, I'm sure with how popular Minecraft has been for quite some time, that they specifically worked on some optimizations with that game in mind. Minecraft isn't exactly the most efficient game. I'm sure getting this extra performance probably took a lot of time and resources, but if something is very popular, sometime it is worth it to try to squeeze out as much performance as possible, or maybe someone saw an optimization that would give a lot of that performance, but it would take months to get it working just right.
Not that I have done all that much 3D programming, but in what I have done, the Adrenaline drivers are a breath of fresh air, and the Nvidia drivers have been my worst nightmare. Actually if it weren't for the nightmare of the Nvidia drivers I probably would be playing around with more 3D programming.