Einstein Relativity is just 3-dimensional + time and if the 5-dimensional Kaluza-Klein compactification theory had opened up the unifying of electromagnetism and gravity, saying that some extra spatial dimension is connected to the quantization of charge, I would suspect that this Kaluza-Klein must be given worth the attention to perhaps develop it in the standard model like how Newton’s was being done with photoelectricity? After all, if Compactification represents electromagnetism and general relativity then in all honesty, Einstein Relativity and String Theory, and even the combination of the two seem inadequate to even support the standard model theorem. Both do not even make any occam’s razor to justify the general relativity. If I were a scientist, I would reopen the case of Compactification and see what I can do there. Just saying and forgive me if ever I’m out of tune 🙂