I think this may simply be an issue of where to hold the remote rather than how well it works. Keep in mind that this is not radio control: all remotes for the D3400 and several other Nikons use Infrared, which essentially means light. If there is no direct line of sight between your remote and the IR receiver built into your camera, well, it's not going to work well, because in that case you can only rely on reflections in hopes of the camera getting triggered.
Take a look at your camera's manual: the IR receiver sits on the FRONT, in the middle of the hand grip area. That means triggering from close behind is not very useful. Instead, hold the remote somewhere off the front side of your camera, just outside of the lens' viewing angle, and it should trigger every single time. I own two ML-L3's and never had a problem with them.
The question why Nikon puts the receiver on the front of the camera puzzles me, though. Like you, DinoExMachina, I don't like having to trigger shots from the front.