We can look at Lewis' Tao, for example, for the similarities in a myriad of cultures (and religions) with regard to ethics. Such discoveries do not even require "sincere and deep inter-faith explorations".
However, to rest our hope of reconciliation on such similarities is a fool's errand. In fact, a sincere and deep inter-faith exploration will result in exactly what the current proponents do not want. That is the illumination of the differences that make the different religions different.
We must not rely on our chronological snobbery that assumes that past generations have failed where we will succeed. They recognized that the differences are significant and really the only attributes that matter. By removing the difference (by whatever means) we will not end up with better religions or even one religion. We will end up with no religions at all.