The problem is that gravity, like EM, follows an inverse-square rule. If gravity had a 4th dimensional component, we would expect to see an inverse-cube situation. The equation is: 1/(1-dimensions)
Re: EM, the Biot-Savart force law can result in long-range attractive forces proportional to d^-1 instead of d^-2. So if it’s operative at galactic and intergalactic scales (between plasma filaments) and we’re not fully taking it into account, then we may be discounting the most powerful long-range force in the universe.
Youtube video that explains this in depth: https://www.youtube.com/watch?v=3HYw6vPR9qU&t=726s