Oh Force Touch, this was one of the biggest UX fails of the modern Apple era. It all goes back to one of Apple's Macintosh era fails: the one button mouse. This was one thing that can be reasonably argued (as I do) that Jobs was wrong about.

Right-clicking became so ubiquitous and even consistent on Windows. You needed the same behaviour on Macs but had no second mouse button so got that by using modifier keys. Some apps it was Option, others control and so on.

The problem was that those modified clicks had no discoverability and less consistency than right-clicking. Windows users on the other hand learned that nothing bad could happen with a right click.

Force Touch as a similar kind of UX fail with no discoverability. There was (and is) no consistency with what a Force Touch means or should mean or even if it's an option at all.

But yes, Force Touch did make the iPhone thicker and heavier.