It seems to me that a big part of the upheaval is in where on the cladogram we draw that line. If we split a species into a clade of several related species, haven’t we merely moved the species boundary further out, that is, from before the branching to after? This is why I find the mushrooms so frustrating. One “field guide species” (for lack of a better term) is split into several species based on gene sequencing; but if those newly split species are all each other’s closest relatives, what is accomplished? The “field guide species” is equivalent to the monophyletic group.