I admit it. I was one of the few people who thought the 3D Touch would turn into something very good when it was first unveiled. Whether you have ever used it or not, it was an interesting concept in that it gave Apple a way to refresh its static Springboard without actually changing the look or overall design.
But the same is also one of the reasons why 3D Touch never reached its full potential. It was hidden behind the same old interface that all iOS users are used to. If you don't train yourself to use it, it's so easy to forget about it yourself.
I have a couple of 3D shortcuts that I use regularly, such as quickly drawing directions to Home or Work in Google Maps (mainly for the traffic update). I also use it a lot for cursor placement when editing text. However, I rarely think of trying it for anything other than these routine tasks. If someone like me who thinks the 3D Touch has any benefit, it almost doesn't take advantage of it, it means that most iPhone users have never tried it.
The biggest downturn to the 3D Touch is that it is not universal across Apple devices. It is a variant of it called Cold Touch, but it doesn't quite work the same. It was never used on the iPad, probably because it was too expensive to include on such large screens. The fact that 3D Touch was never a universal standard ensured that developers would never completely embrace it. There was no real incentive for them to go beyond the most basic implementation.
One thing I like about 3D Touch is how good it worked from a hardware perspective. Apple blows away the competition when it comes to haptic feedback. They are extremely smooth and accurate, making 3D Touch easy enough to use for the chance someone actually remembers it. I will miss that part of it.
The good thing is that even though 3D Touch probably goes away, Apple will still retain much of the basic functionality of the IOS by using long press to trigger a simple haptic press. They have already implemented this on the iPad and it works well enough. At least in the future, most Apple mobile devices will be more united in how they handle presses and cranes, which should cut back on confusion. It's always a good thing.