iOS 12 beta finally lets you get the same function by holding down on spacebar, for non 3d-touch phones.

Almost. This lets you move the insertion point, but AFAIK there's no replacement for the 3D Touch feature wherein you can push in again while moving the cursor to select the word (and again to select the whole line).

I have 3D Touch and use this handy cursor all the time but I would welcome a transition to a hold down on the spacebar. 3D Touch doesn’t always fire when I press down hard and I wish it was more reliable to enable. Using the hard press always makes me worry I’m going to either drop my phone or crack the glass.

Because it doesn’t always fire my muscle memory has evolved to just press down harder to increase reliability. And it’s still only sees 90% of my hard presses.

I think you can change the pressure for Force Touch or 3D Touch under Settings > General > Accessibility

This was already present in some 3d keyboards (gboard, for one).

Whoa! So outdated! That thing existed on LG G2.