One of the issues with the 3D Touch replacement (“long press”) is that if I accidentally hold a finger on the screen for too long (e.g. I’m touching lightly to scroll, but pausing for a moment to finish reading), then I’m unintentionally long pressing something. This wouldn’t happen with 3D Touch.

Another one is that the illusion of pressing a tactile button is gone. 3D Touch would give tactile feedback only if the screen was pressed with force; this was realistic enough to simulate actual buttons on iphone7/8. The long press has no way of measuring force, so it accepts light touch too and still responds with haptic feedback; this doesn’t happen in the real world and the illusion is gone.