I mean, it’s not completely gone, if somebody wants a supporting iPhone model like the iPhone 8, you can still have 3D Touch, you just obviously lack certain things like Face ID and new advancements.
But for those who actually truly understood how 3D Touch was operated, it really was a useful feature. But I also think the writing was on the wall for 3D Touch for quite some time, being even third-party developers stop supporting certain peak/pop features, given Apple never really marketed 3D Touch the way they should have from the beginning, similar to ‘Live Photo’s’.